oooooops
OP, in that case use the default wifi power settings. Also I'm sure you'll be tempted to use the max 30db just to see what happens, well sometimes too much wifi power is bad and you probably won't be able to connect any devices (at least on 5ghz band). This is what happened when I moved the slider on my Asus RT-AC5300 all the way to 100% (for testing purposes).
This is the db value>mW power correlation on my AC5300 (taken from readme notes on Hugo Gomes' 380.63 firmware)
1% => 30mW (13.2dBm + 1.5dBm[AG] = 14.7dBm)
25% => 119mW (19.2dBm + 1.5dBm[AG] = 20.7dBm)
50% => 251mW (22.5dBm + 1.5dBm[AG] = 24dBm)
75% => 531mW (25.7dBm + 1.5dBm[AG] = 27.2dBm)
100% => 1000mW (28.5dBm + 1.5dBm[AG] = 30dBm)
Also worth reading this excellent article for a better understanding of wifi power levels:
http://quantenna.wpengine.com/wp-content/uploads/2016/08/80211nPowerSettings.pdf