I just taught the scc SLOC tool I use how to detect and recognize the Mu programming language. So it's actually a bit worse than your estimate. It's more like ~60/30 at the moment:

>>> mu = 1445
>>> asm = 2365
>>> T = mu + asm
>>> mu / T * 100
37.9265091863517
>>> asm / T * 100
62.07349081364829