Maximum FlagEncoders

How can i check previously how many FlagEncodres I can use?
I downloaded graphhopper and wanted to try out all available Flagencoders locally and I have already set graph.bytesForFlags=8, but I recieve this Exception.

INFORMATION: An exception was caught and reported. Message: java.lang.IllegalArgumentException: Encoders are requesting more than 64 bits of way flags. Decrease the number of vehicles or increase the flags to take long via graph.bytesForFlags=8

That is not possible up front except from adding catching the exception. What is the use case?