Income / fee fiat price discrepancy

Hi Im trying to get my head around the tax reporting for UK. I noticed that the Koinly report is showing differences between the income BTC price and the Fee BTC price.

See image: https://ibb.co/t8p3kX5

My questions are:

Is this correct…
And, when are the values calculated… (time of transaction, time of reporting, daily high/average/low)

Any help would be appreciated