Please be sure to check out Geoclaim Contest Rules for full details about this feature in general.
The ownership percentage (%) is the likelihood that you will be selected for any given Geomine in that Geoclaim area.
Every Geomine rewards a variable amount of COIN based on several factors, so you may be selected for a Big Geomine or you may be selected for a very small Geomine, or anything in between.
As a result, you can't expect the percentage (%) ownership to calculate the expected earnings since for example, one Geomine could have generated half the COIN earned as Geoclaim rewards in an area.
Geoclaims are a game of balance between how much to spend on ownership and how much you can earn back. Some areas may reward better than others, so it is best to experiment rather than spend all your COIN on each Geoclaim available.
When do I get my Geoclaim rewards?