even if I suck at calculator.
it was happening.
I was being charged 1.3% each trade.
Yeah, I really believe you now. Especially since you've such a great grasp of mathematics and how mt gox takes commission.
when I noticed it I typed "25 minus 0.65%" into google.
the result was different than my logbook, it didn't make sense.
so i typed "25 minus 1.3%" and it matched.
I don't care if you believe me or not.
If Mt. Gox still has the CSV associated with my account I'll show you.
"25 minus 1.3%" gives you the wrong value, you need to type "25 minus 1.3% of 25". So if your story is true, it does not mean that mt gox was charging 1.3%. You just got your numbers wrong.
Honestly, the google thing looks like a bug. It should be able to calculate "25 minus 1.3%" correctly. So it isn't completely your fault.
Did your trades happen to be for 2 btc, because if so then your story checks out, the numbers are just wrong because of google.