200bit numbers only require like 10 registers. X86-64 has 16 general purpose registers so doing operations with 200 digit numbers should hypothetically only require 20 loads and 10 multiplies. So a well written bit of code could do it in under 100 ops (probably under 50). So assuming this LLM implementation is running on a big server, it's probably doing the same calculation, less accurately, with some exponentially larger amount of operations.