You changed tier between the 8th and 13th August but only played some CTTH for a while. Your new average is based on the 38's on BOP 4 and Merion F9, these are your only ranked rounds as Master.
It's not really a penalty, or not much anyway...but hard to explain without formatting.....
After 40 ranked rounds as Master any good scores will replace your worst one, all that'll ever make up your average is your 40 best scores (in ranked rounds) from when you tiered up....... So hopefully the 38's will quickly be discarded.