Different file size after upload a file

Hi all,

Thank you very much in advance for helping.

I've observed that every time I synchronise a directory, some files always needed to be updated.
Look closely, I noticed that the reason why this happens is because the file size is different.
So a 610Kb file in my computer, it transformed into 593Kb when I upload it to the server.
It happens with xml and js files.

Any idea why this happens?

Thanks

Update:

I have changed:
Preferences > Transfer > Edit > Transfer mode
from 'Autamatic' to 'Binary' and now the file transfer with the right size.

Cheers