Clearly with the scores you got on the 6th and 7th you mean why didn't your average go up, the answers that immediately follow confuse me.
To be promoted from TM to Legend you need an average of 61 over 50 ranked rounds at that tier (TM).
When you've played 50 rounds at TM you are saturated, that means your average is no longer a true average of your rounds at TM but becomes an average of your 50 best rounds. At that point it can no longer go up as any round that's worse (than the highest score included in the 50) is disregarded. It does mean a score of 62 could drop your average (as said immediately above) and a 61 always will, but nothing will make it get higher (until you're a Legend).
Edit: Seems I was completely wrong and you were expecting your average to go down (not sure how I missed these posts, maybe moderation delays) but I'll leave the above anyway as the description of how tier progression works may be a little help to someone and also, I complain about others changing what they said.