There is not enough space on http://myCompany.com. You need an additional 13,4 GB to copy these files

I am using sp 2010 and try to copy a lot of files to a document library by the file explorer. I got this error:

There is not enough space on http://myCompany.com. You need an additional 13,4 GB to copy these files

I try to upload only small parts and only the first 3 parts worked. The fourth part give me again the same error but with another gb value:

There is not enough space on http://myCompany.com. You need an additional 2,4 GB to copy these files

What is going wrong? I do not have a site collection quota!

UPDATE! here is a printscreen of the site collection quota. There is no limit.