All right guys. Here you are. The evidence
It's double scaled: red and black numbers.
Sailor Steve, you misunderstood me, not the ingame tool is useless but the reallife protractor, if it would be round. But as we can see, it's not round. By the way, i also played sh3 GWX for several years.
It was just a suggestion to make the second scale to improve this tool's functionality. It will be neded if you want to mark the player sub's position on chart manualy using landmarks, when playing with "real navigation".
Best regards.