I am not familiar with "ibrewmaster"
Are you batch sparging? If so, 30 min is too long.
If you know what you want , why do you have to "calculate" it?
Wayne Gretzky-"100% of the shots you don't take, don't go in
Revvy>>You shouldn't worry about ANYTHING, you didn't hurt the yeast, they know what they need to do, they want to eat all that sugar they are swimming around in. They want to pee alcohol and fart co2, it's their nature.
Bobby_M>>I flood the keg with CO2 for one minute with the lid off, rack the beer in to the bottom gently, seal it, flood it, vent it. If there's still O2 in there after that, F it.