That all looks right.
That expected time is in seconds, and 586991 / 3600.0 / 24 = 6.79 days
You should stake once every 7 days or so. You haven't staked at all in 23 days. That's unlucky.
Take a look at your debug.log file - it's in the same folder as your CLAM wallet.dat.
Do you see something like this?
CWallet::CreateCoinStake() found no stake
stake took 3s
starting stake
CWallet::CreateCoinStake() found no stake
stake took 4s
If so, what do the "stake took ..." lines say? If it's more than 16 seconds that's a problem.