A question to folks from other countries about paypal

I have this site I do, and people have been showing their payment proofs, however I noticed something strange about it. It's all in USD but for $1.00 they have it like this $1,00 is that normal? For USD in other countries?? The . should be there not a , which is why I am wondering if the proofs they are showing is real or not.

I know I am about ready to head to bed here but would love to know why it is that way. And if I scoot off to bed I will reply in the morning. Thanks all for any responses.