I have not done a lot of work on outboards... but I have seen that large amount of advance rotation for the ignition... I don't know why they need so much.
But as far as checking it.... I would think you would use a strobe ignition timing light and look for marks on the flywheel and see if they line up while idling... there might be another mark for full advance also.
If you are trying to set it before it is ready to run... just set it near where it was (or in the middle?)... because with such a wide variation it should run almost anywhere you put it... then strobe check it and adjust it to suit.
I also have a neighbor who's home operated business is outboard repair.. and any questions can easily be answered by him if need be... he does cylinder boring and honing and boat motor warranty work for dealers also
This is the guy who has all the tools for bore and hone's on small bore ped engines.