That's on the maser branch right now, no idea how branching works for this project but we can probably assume the numbers are ascending from minimum up.
The ATA/ATAPI sub-command for setting the level of AAM operation is an 8-bit value from 0 to 255. Most modern drives ship with the vendor-defined value of 0x00 in the acoustic management setting. This often translates to the max-performance value of 254 stated in the standard. Values between 128 and 254 (0x80 - 0xFE) enable the feature and select most-quiet to most-performance settings along that range.
It sounds like Maximum is the quietest. But wikipedia is also saying the feature isn't even enabled until 128, so I am not sure what might be going. For my system I personally don't hear a difference between MINIMUM or MAXIMUM.