Roasting color issues

Hi everyone, I’m having issues to match light roast in both sides of the beans. When i measured the whole bean im getting 60 agtron level and ground bean 80 agtron level. I thinks There’s a big different so anyone can chare some tips how to avoid it?
Maybe I’m preheating to high? Maybe i need more airflow? Drum speed?
My batches sizes is 350gr 220c ph P0 (soaking for a minute)P6 f2 d9
I’m sharing my last roast.

Thanks.

What bean are you roasting, how was it processed and what level are you roasting to?

It would also be good to confirm how you’re measuring the ground sample-- espresso grind, well tamped, for example?

in this case its a washed bourbon from guatemala I want to do a light roast

I’m doing filter grind (23 clicks on the el comandante grinder). Last day I was reading rao and he was saying to grind fine for the test. I did las time and now I have 95 agtron level, so I have more difference than before

Hey-not being critical here.
I’ve found that I need a little more momentum in the roast to bring the interior and exterior colors closer together. So, what I would do would be to charge say 5C hotter or go to 7H, stay there 5-10C longer then make cuts. Goal is a little steeper slope. FWIW, I aim for a 7C-8C FC delta at 14%-16% for a light roast.
Also FWIW and FYI, just in case you weren’t aware, the bean mass probe reads a lot differently at really small batch sizes. You’re roasting about 1/3. I understand you’re probably working out samples for production but it’ll change as you scale up. Good luck.