Logs uploading inaccurately

So everytime I upload my logs from wow, the dps of every single person in the raid is bumped up about 200-300k more than the people actually pulled on the fight according to details or other peoples logs. This didnt happen to me back in nighthold, but sometime in tomb it changed and has been that way ever since. For example last night I had a 2.04m parse on heroic garothi in Antorus, but when I upload the log, it says I did 2.35m. Any ideas whats causing this and how to fix it?

Is your system clock broken and accelerating time?

Sorry to get back to this so late, I pretty much gave up on it for a while and let a guildie log everything. However I did notice my logs are shorter than the correct ones, for example we had a 4:09 Varimathras kill, my log said 3:35. Now my system clock was correct, so im not sure whats happening there. I tried changing the link to where my computer updates the time from but havnt tested if that fixed it. Is there any other way to fix this that you know of just incase that didnt work?