The story is:
After I set MCS parameter to 8 as below:

then, the data rate of STA shows Tx=5.5, Rx=39.0, as you can see below:
Isn't the data rate supposed to be 14 Mbps@MCS 8(20MHz, short GI)?
How's the values 5.5 / 39 would happen?
Would anyone could explain it please?
Thank you very much.