Hi, Please don't think your question is silly. When you get these pieces of information it's hard to take it in.
If it was me I'd now want to know how they know that, was it that diameter on the outer edge of the margin for example, although I'm not sure what difference it makes if it's a fact.
I'd also be wanting to know what further treatment they're offering and when. Is another MRI or other test offered? What is the next psa test going to mean even if it's very low or it's higher.
As others have said hormones and radiotherapy seem an option and if it was me I'd be asking for the plan for when it starts and be wanting it to start.
We're all different in how we react so you might have other ideas as will others, and there might be other options.
I'd think it's good to have had the operation and now to get those remnants sorted.