@ Asker 05:13 Jun 12, 2013
I'm sure you're aware that the EN in your source text is seriously flawed — almost certainly non-native.
Everything here hinges, not around the term 'limit', but rather, around the term 'period'; if it is being used accurately, then it would normally be describing the period of time during which downloading is possible — the 'window' if you like. But in view of the rest of the text, Anthony's interpretation certainly makes more sense: that it is talking about the actual time taken to perfrom the synchronization; normally, in EN, we wouldn't have called this 'period', but probably, for example, 'time'.
So you may need to try and glean other clues from the rest of your text to try and clear up the ambiguity. | 
