Question about timing of post meal glucose check

J

I was just diagnosed with GD last week and haven’t had a chance to see my midwife to ask a few detailed questions. I’ve already started monitoring though, but have a question. If I get home and need a snack before dinner (whole wheat cracker and cheese) about 1-1.5 hr before dinner, is that going to affect my 1 hr post dinner reading? Or do I still just measure from an hour after I start my actual dinner? Thanks all!