Do they get 10s from their original time, or 10s are added from when they moved.
Example of what I mean (since its probably not clear).
Lets say its the person's move and they have 50 seconds left, is what happens something like:
1) They seem to make in, lets say, two seconds and should have 48 seconds left but instead have more than 50?
2) They seem to make a move after, lets say, 20 seconds and should have 30 seconds left, but instead have 40 seconds left?
If its 1) its cheating, if its 2) thats is (probably) due to lag, it may have seemed like they took the 20 seconds to make the move but it really took them 10, but it took an additional 10 seconds for it to get registered.
What I mean, is that if it never happens that a player has more time after they make a move than before, then its probably not cheating.