Stupid count question

I have some galleries. The site owner asked me to order them by the date they were added DESC. No problem so far. But they should be numbered (ASC) as well ( numbers are displayed on the thumbnail)! Before I ordered them by id ASC so could simply use the id as the number but now I can’t use this any longer, and I can’t get my head around it how I get those numbers going from 1 till the number available while number 1 is actually the last record.

I have this one solved in my server side scripting. Thanks