To see how the COIN subscriptions can boost COIN collection, please see https://coinapp.co/plans/
To predict how much you could earn before upgrading, please see Is there a way to predict my COIN earnings?
If you think your subscription plan is not rewarding you correctly, make sure your Premium subscription is active on your account. Please take a look at your profile window in the top left corner. You should be able to see which premium plan you are subscribed to. If your account is Basic when you know your account should be upgraded, please see Downgraded/missing subscription Help
You can see less than the expected minimum of 0.26 COIN(Plus) 0.36 COIN(Pro) for a couple of different reasons. The most likely one is using different devices with the same account, which can reduce rewards to deter exploitation of the rewards system.
Another factor is re-Geomining an already Geomined tile (that was Geomined by another user or another account of yours). In addition, if you were referred by another user, they are getting 10% of your geomining rewards which can reduce the minimum below the expected 0.36 COIN(Pro)
The best practice is to have only one device logged in with your Pro account. You can create other unique accounts for other devices you want to use for Geomining if you want to use multiple phones at any given time.