Two different numbers - 30 seconds apart

So I have been self monitoring my BG as Dr says I have GD but specialist and dietrician were happy with me just to adjust my diet. (Reduce carbs, increase proteins)

I have had perfect numbers all week, here are some examples:

Roast Chicken, roast potatoes and veg - 95mg two hours after

Cereal - 112mg one hour after

Chilli con carne - 106 two hours after

Fasting have been around 88-90mg

This morning I had a fasting reading of 96mg and I was quite surprised so I retested immediately and it went down to 88mg.

My issue is I want the 88mg to be the correct one as 96mg is just outside of the ranges I've been told but which one is actually accurate?

Thanks

Becki