I have 5,000iu vials that I add 5ml bac water to mix up. To get 500 units in a 1ml syringe, I would fill it half way to the 5 on the syringe. You have a 10,000iu bottle (double mine) so I assume that you would take half the volume, 2.5 in the syringe.
The official protocol I’m prescribed is...