If you’ve successfully generated a block, you’ve seen it has a maturation countdown before you can spend it. Once it matures, the Credit column will change from 0.00 to 50.00. For a block to be valid, it has to be broadcasted to the network and get into the block chain, which is why Generate does not run if you’re not connected. If you generated a block without being connected, the network wouldn’t know about it and would continue building the chain without it, leaving it behind, and the maturation countdown would change to “(not accepted)” when your node sees that it wasn’t used. If you subtract 1 from the status column, that’s how many blocks have been chained after yours.