Excellent news Corinne!
If we're talking about the 23l tank here (actually it's more of a cup than a tank!

) ten is the maximum I would put in there and that's if they're all males, the females are larger. But they should be put in first before the shrimp. In such a small tank I would only put five in to start and then a week or two later the other five (keeping a close eye on water parameters for a few days after). The shrimps should then be put in a couple of weeks after that when you're certain the tank is stable.
Personally though I think it's such a small tank that I wouldn't go above six male endler's and a few shrimp.