From the description I thought the expression was a function of only 't', and there was no (for instance) accumulation of the previously computed byte. Then in the image I saw the same value of 't' evaluating to different values:

t=1000: 168 t=1000: 80

Reading the source: https://github.com/KMJ-007/zigbeat/blob/main/src/evaluator.z...

It does look like the expression is a pure function of 't', so I can only assume that's a typo.