Buying credits, Buy per vehicle or ECM model?

I was looking to buy some credits for my HP tuners but had a question. The engine I have is from a 2019 Gen 5 5.3 Silverado. That came with an E90 ECM. At the time, those were locked. The guy who made my harness for the engine made everything to go with an E92 ECM. Do I buy a credit for the ECM? Would that be a 2018?

Thanks.

read the ecm for starters. Universal credits can be used on any application/ecm that we support.