Archer C7 v.4 Transmit Power calculation includes all three antennas?

Hello! I am trying to figure out if this i am facing right now is a bug or i don't understand how it works.

I want to set maximum transmit power on my Archer C7 v2 (OpenWrt 19.07.4) and in my country (Greece) maximum transmit power is 20db/100mw. If i set transmit power to 20db it automatically goes to 17db cause maybe it counts the +3dbi of a typical antenna. This specific version 4 has a total of three external antennas. If the firmware count only 1 antenna as 3bi then total transmit power would be way over than my country's limit.
Please correct me if i am wrong. All i need is to have a maximum of transmit power (including antennas dbi) of 17db/50mw.

select USA as country, then save & apply, and try max power level again.

for me, I have 24dB max power for 2.4GHz and 23dB for 5GHz, set as fixed.

Thanks for replying. Yes if I change to USA it gives me the option to select 24dbm. The thing is that I want to reduce the total power. Let's say that I stay at my country's regulated option and select transmit power 17dbm. Does open wrt calculate the 9dbi of the three antenna the archer v4 has? Cause I have a unifi ac lr and if I choose 17dbm it adds another 3dbi of the antenna and the total is 20dbm/100mw which is my country's maximum allowed E.I.R.P. I don't want to go over 50mw cause I don't have wifi clients that can talk back to the ap. I think that open wrt on this model counts only 1 antenna that's why it maxes out at 17 dbm. (17dbm + 3dbi) from antenna 20 db E.I.R.P.