If you use older semi postal stamps for mailing, and say the stamp is 10¢ + 5¢, do you get credit for 10 cents postage or 15 cents postage and would postal employees know.
Pocomo is correct the postage value is the first 10c value. My addition is that you will find PO employees that also do not understand that despite the fact that they sell semipostal stamps today (63 + 10c). Even if a given PO employee lets them through on the sending end as 15c I don't suggest doing it because the PO employee on the other end may know the rules and you don't want the buyer getting dinged for postage due charges.....over a 5c "saving"....
