This command creates power supplies where the number of power supplies are minimized, assigning the same power supply to multiple letters where possible.
The level of granularity for this feature is the letter, meaning that a letter will not be split between two power supplies.
In this example we have four power supplies across seven letters. The "T" and "I" are together on one power supply with a load of only 51%, but the "M" would not also fit, so it gets its own power supply.