Why my products disappears from download?

[floriano]

I need help, my site is: az-download.com .

 

I want to upload new products for download.

 

But I don't know what must setting in: Number of allowed downloads ---- Number of downloads allowed per customer. (Set to 0 for unlimited downloads)???

 

But I must set character "o" or number "0" ?

 

I upload products for downloads but after some days I have not have products in "associated file"

Why my product disappears after a few days?

"Leave blank if you do not wish to attach an expiration date"

I don't write anything to date, let loose (empty space).

 

I put an example in picture.

ts in: "Does this product have an associated file?"

 

 

 

Thanks in advance!