We have been down this fuel delivery road many times on this site.
I don't want to rehash this again, but I have a lot of experience with melted pistons and so have many others on this site.
In the past I did my flow test using just the starter. The problem with this method is that there were a lot of different set ups. It depended on your starter condition and your battery condition. A weak starter or battery gave suspect results. We (I) now do it at IDLE.
Flow rate:
I do it at 4.5oz in 10 sec at Idle.
If you are getting less than this you are in dangerous territory.
At wide open throttle you could get a lean out and melt a piston.
As for the 50cc you see in the manual it could be a typo. There have been other typo's in the various manuals so I would just disregard that.
Also of note is that the fuel system on an FL350 and FL400 has a bypass "T" that goes to tank. Excessive fuel flow goes to tank. Therefore the more flow the better to prevent a lean out condition and melted piston.
I have a couple of videos and youtube about this:
https://www.youtube.com/watch?v=WT-rBlEb8Z4Do what you want, it's your machine but I run 4.5oz in 10 sec at idle.
Also of note: AVGAS
You are on your own if you don't listen.
CO