Does anyone know or understand what the relation (technically) is between limit_req & burst value and limit_req_zone & rate value?

It seems that burst must be equal to rate, if less rate is triggered to fail (excess 1.000) and sticks to this excess value forever.

ea. is there a relation to the local timer event/count?

ai. when using a rate=32 without using burst, excess is fairly quick reached no matter how high rate is set (timing issue??)
when adding a burst value like 16 excess is less often reached but still happens on less then rate value connections.
when using burst value=rate excess exactly works as intended, which is odd unless the technical design was intended as such(ea. the requirement to use them both) and brings me back to the question I started with.