I agree with seesaw here, there may be things that you dont know about the situation... example before I had my home employment that I have now I worked for a company where sometimes i got calls about work issues during my home hours. obviously Im not going to drive in to work at 3 am just to make out a time sheet. I kept track of how much time I have put in on work issues during my home time then when i go in to work I fill in the time sheet as required. my workers were not privy to when I was working on work issues at home or not, sometimes they saw me doing they they thought was my marking my time sheets adding more time then they witnessed. one actually got fired because they were paying more attention to their co workers time sheets and work then they were focusing on their own time sheets and work.

my suggestion if it really bothers you sure you can go to your supervisors, Im not here to say whether you should or shouldnt do something.

but maybe in this also take into consideration that just because you ......see..... them filling out their time sheets according to what.........you.....may feel is wrong way to do it, may not be the whole story. there may be things that you do not know about the situation.