Thank you for your post! You are correct, if you import 2 maps, then delete 2 maps, you will be able to import 2 more maps. If you are using the app for recreational purposes, there is a subscription ‘Unlock Map Imports’ which will allow you to import an unlimited number of your own maps. If you are using the app for non-recreational purposes, then you require a Pro subscription which includes unlimited custom map imports, shapefile support, and other Pro specific features. If you are interested in purchasing a subscription, you can do so in the app by going to Settings > Upgrade Account.
If you have further questions please let me know!