Gas Pipe Size Calculation for Tankless Heater

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new Jersey
I'm looking to install a Navien 240 NPEA2 that use 199k BTUs. My plumber thinks my gas lines will work fine, but I wanted to double check as he didn't actually measure anything.

I have a 40 feet 1in gas pipe coming from the meter and then a 10 feet 0.75in branch coming off that. I don't have any other appliances on that branch. If I consult a gas chart and look at the 50 feet row, and 0.75inch pipe would only provide me 151 cu ft. of BTU capacity. However is this too conservative since 40 ft of line was from a 1in pipe?

In case its helpful to know, my water meter has a 415 CFH.
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