So for instance if the second number you had to memorize was say 53, then you can picture Elizabeth II riding a lama (because "lama" is 53 in the major system), or you can think of the sentence "the queen is lame". I personally like using images of animals, but to each his own.
If this works for you, that's quite impressive. But to me, it seems like a lot more work and a lot more difficult than just converting the seed into 12 or even 24 words and memorizing those. Elizabeth could just as well be a mummy (33) or boss (90).
It gets even more confusing when you have more than one seed to remember.
The entropy size for BIP32 is between 16 and 64 bytes and I believe the seed that bitcoin core uses is actually 256 bits which means if you convert it with your scheme you should end up with at least 70 values.
Each number has 2 decimal digits, that's how it ends up at 38.
Our memory as humans is absolutely awful
~
this shouldn't be the only way that you are remembering your private key
Years ago, I hid a paper wallet somewhere in the house before going on vacation, and despite searching everywhere, I never found it back. But indeed it wasn't my only storage method, so I didn't lose anything. I can remember some things for years without problems, while instantly forgetting some very obvious other things.