You mean MBT? That's minimum timing for best torque, sometime called maximum brake torque and is the amount of ignition advance that will yield the best torque or power the engine can make. Often times you will be knock limited meaning you'll get knock/detonation before reaching MBT. If not, if you increase timing past MBT you'll plateau and lose power and nitrous oxide emissions will skyrocket.
The physical engine characteristics heavily influence MBT such as the overall volumetric efficiency (VE), the piston dome/crown design, combustion chamber shape, valvetrain, fuel used, etc. Most tuners (actually creating calibration/tunes altering tables and setting in the computer and not just tweaking settings on a handheld flasher) will generally try to run as much timing as the fuel octane will allow and get as close to MBT timing range, but if the engine has been altered or in some cases where timing is increased over MBT it is possible to lose power with too much timing but you need to do a lot of testing on a loading dyno to determine if that's the case at any points in the power curve.
Eric H. - '04 Neon SRT-4 (eBlue/S2) - '04 SRT-4 (blk/stock)
'92 Dodge Daytona IROC R/T --
'91 Dodge Spirit R/T
plus a couple other turbo Dodges, a Cobalt, a couple Focus, a V-wagon, and some other stuff...