If EACs only cover part of my electricity emissions, can I subtract that amount from my total market-based Scope 2 emissions?

Yes, that’s right. If your electricity use causes 50 tons of CO₂ and you buy EACs that cover 10 tons, you can report 40 tons under the market-based method. The EACs reduce only the part they cover, and the rest stays as reported emissions unless you buy more.