Pheonix, it all depends on how much solution you are using to reconstitute the HCG.
Here's an easy no-brainer way to determine.
1.Use a regular 3cc pin to withdraw the solution.
2.Notice how many cc's of solution you have (with my 5000iu kits, I get 1 cc of solution so 500iu's would be 10 on a slin pin.)
3.If you are using 3cc's of solution for every 15000iu's you will fill the slin pin to 10.
4.If you are using 2cc's of Solution for every 150000iu's you will roughly be around 6iu's on the slin pin.
Hope this helps...