Flow Test with Higher Residual than Static

Had an experienced fire sprinkler contractor run a flow test in a semi-remote area (outside of a large metro area) with a higher residual pressure (45 psi) than static (42 psi). The static pressure was confirmed both before and after the flow test. The flow was relatively low (410 gpm using a 1-3/4" pitoless little hose monster).

I've yet to come across a scenario like this before - could this be due to the city's pumps kicking on during the test, or something else? Wondering if anyone had experience in this regard before.

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