What does 'Offline Expires in' mean? Why does it say my license is going to expire?

The Offline Expires in column shown in the Maxon App is the amount of offline time available to you should you disconnect from the internet.

Only when you are disconnected from the internet will this start to count down. This offline functionality is automatically activated when a disconnect occurs.

Offline use does not affect your usage of the product whatsoever until 7 days have passed. 

The Offline Expires in timer has no effect on when a subscription renews/expires.