I received a vial of HCG that says 10000 I.U. / 1 mil. I have insulin syringes that have the lowest number at 10 and the highest at 100. I m supposed to take 500 IU. What number on the syringe do I draw it back to? Everything I read online keeps confusing me even more. I just want to know if I draw it to 10, 20, 30, 40, or 50, etc.