Nothing adds to the trims or makes them go higher or lower, it's just going off your airflow tables are different loads/rpm and your o2 sensor are seeing it.

You could try to pinpoint exactly what MAF hz you are at while cruising speeds and go in your MAF curve and add like 1-2% in that small section to see if the trims drop.

I honestly wouldn't even care if there were like that, it's not going to change how it drives or hurt mileage if it randomly bumps up to around +7-9.