Its 30 Coins for every block regardless of the size of the block, up to a maximum of 14 day coinage, the smallest blocks I have seen stake lately were around 300 coins but that might be a little misleading because the default stake theshold is 500 but I doubt anyone changes it. Most blocks are between 500-1000 that are currently staking, smaller blocks would take longer but yeild a higher % reward, larger blocks will stake sooner and can compound a little.
Hope this helps