Thanks for the PR. Looking back from history, this limit was last touched around 11 years ago in issue #6. Sadly that's missing the information why or how I ended up with the current value of 50000. I'll have to dig some more to see if I can find the reason, just in case there's something extra to it other than just increasing the limit.

I wasn't able to find the reasoning how that 5000 ended up being the current value. https://github.com/vergoh/vnstat/blob/master/src/cfg.c#L311 is one part of related implementation when BWMAX is changed but due to UPDATEINTERVAL being used as fallback value, this will not result in an update interval lower than 10 seconds even if a maximum bandwidth of 400 Gbit gets detected or set. So all should be fine on that front.