Filezilla does not download all files

[AndreaeNoemi]

Hello to all!
I want to back up files from my website to my computer.

I used Filezilla to download all files from the server to my computer. I repeated this operation three times. Every time I get a different amount of files!

Why is this? How do I download ALL the files? I want to be sure of that! There is a limit to another program?

Thanks!