Basically every log parser out there agrees that Glyps of PW:S healed 64 times in this fight, so one can assume that PW:S was used 64 times. But that's where interesting stuff happens. Here's a small breakdown for the number of PW:S\GoPW:S : WoL - 191\64 , RL - 156\64 , WMO - 190\64 , MMO-L - 182\64 and only EHFS makes sense with 64\64 since there it now way a priest can cast 150+ PW:S and 83 PoH and do other stuff in the course of a six and a half min fight.
Also the values of absorbs wary and sometimes dramatically. Also no one except EHFS count shaman Ancestral Fortitude as an absorb\damage negation mechanic along with DK's shields and Bear absorption shields that proc whe you crit. Basically I want to know why they do not count this mechanics and what's up with absorption counts.
The basic method for tracking shields is that every time a shield on someone changes, the log reports the new value. Going from 0 to x is a shield being applied. Going from x to y where y<x is an absorb. Going from x to y where y>x is a shield increase (e.g. Divine Aegis accumulating). A shield aura expiring is the shield timing out. Usually it's simplest in terms of merging this mechanic into combat logger frameworks to count every absorb as a separate heal, and any timing out shield as overhealing. There's no obligation to report things this way - you could add every Power Word: Shield absorb to the previously cast application if you wanted, but then you might run into trouble trying to deal with Divine Aegis repeatedly being applied to a target and the shield total moving up and down without reaching zero for a period. It's generally assumed that if you want to know how many shields were cast
rather than how many times shields absorbed
you can find that some other way - number of glyph heals is an obvious route, but cast numbers can be separately reported (this is also a sensible thing to do if you want to look at casts of hots, versus ticks of hots as an example).
Mitigation mechanics are never reported this way. I don't know how EHFS chooses to calculate it, but if you have the buff (Inspiration or Ancestral Healing) applied you could simply work out how much damage must have been mitigated if the damage caused was physical. Basically a mitigation mechanic will act more like armor - it means you get hit less hard, not that some damage is absorbed.
Bear and DK shields just aren't reported right. As an example - here's some lines for a Blood Shield application:
1/12 19:12:54.891 SPELL_AURA_APPLIED,0x0100000002507FF9,"Fred",0x40514,0x0100000002507FF9,"Fred",0x40514,77535,"Blood Shield",0x8,BUFF
1/12 19:12:58.126 SPELL_AURA_REFRESH,0x0100000002507FF9,"Fred",0x50514,0x0100000002507FF9,"Fred",0x50514,77535,"Blood Shield",0x8,BUFF
1/12 19:13:02.138 SPELL_AURA_REMOVED,0x0100000002507FF9,"Fred",0x40514,0x0100000002507FF9,"Fred",0x40514,77535,"Blood Shield",0x8,BUFF
As a comparison, here's some PW:S lines:
1/12 19:33:05.701 SPELL_CAST_SUCCESS,0x0100000000029AC2,"Asclonus",0x511,0x0100000002163F70,"Fred",0x512,17,"Power Word: Shield",0x2
1/12 19:33:05.884 SPELL_AURA_APPLIED,0x0100000000029AC2,"Asclonus",0x511,0x0100000002163F70,"Fred",0x512,17,"Power Word: Shield",0x2,BUFF,8234,0,0
1/12 19:33:13.972 SPELL_AURA_REFRESH,0x0100000000029AC2,"Asclonus",0x511,0x0100000002163F70,"Fred",0x200512,17,"Power Word: Shield",0x2,BUFF,7207,0,0
1/12 19:33:14.755 SPELL_AURA_REMOVED,0x0100000000029AC2,"Asclonus",0x511,0x0100000002163F70,"Fred",0x200512,17,"Power Word: Shield",0x2,BUFF,0,0,0
The first is the cast of the shield - these are the events you count to figure out how many times it is cast by a priest. The second is the shield value application - note how after the BUFF there's three more values. The first is the new value of the shield and the second two are unused (as far as I know). These values just aren't reported for bear and DK shielding. Nothing we can do about that as log parser authors I'm afraid, just as there's nothing we can do about shadowy apparitions not being linked to their parent shadow priests (I assume that one's not been fixed still as well). After that comes one update showing a partial absorb, and finally it falling off with everything being absorbed (if it had still got some left it would have a value at the end like the refreshes).
Essentially how you report a PW:S heal is a personal choice by the log parser authors - all the logs are reporting the same info, just not in the same format (except EHFS doing Ancestral Healing calculations). Bear and DK shield info isn't given to us by Blizzard. As far as I can tell it's basically impossible to calculate Power Word: Barrier's effects too.