minimum load: convoy will not depart the station until it has been loaded by X%
month wait time: maximum amount of time convoy will wait for the above to happen before it departs.
100%, 1/1: Depart when capacity is 100% or depart after waiting for a full month
100%, 1/2: Depart when capacity is 100% or depart after waiting for a half month
100%, 1/4: Depart when capacity is 100% or depart after waiting for a quarter month
etc.
Best to try it out in a freeplay game.
Typically, for buses and other lower capacity vehicles, you will want to use shorter intervals of 1/16, 1/32, etc.
For high capacity vehicles, like ships, you will want to use longer intervals, like 1/2, 1/4.
Of course, those are not rules by any means.