Groups in the MAtricks are used to separate the selection into the number of groups set.
It alternates through the selection putting fixtures into each group.
It is best explained with an example.
In this example, there are ten fixtures (1 through 10).
They are selected from 1 to 10 without any specific grid information. Highlight is activated.
Since there is no grid information, then the fixtures are only in one axis - the X axis.
Press Next to make the MAtricks X value 0.
It looks like this in the Selection Grid and Fixture Sheet (Channel SheetMode) window:
Now tap + in the XGroup in the MAtricks window to set the value to two.
Now it looks like this:
Notice how the ten fixtures are moved into two boxes in the selection grid.
The fixture sheet shows how the fixtures are interleaved into the two groups. The first fixture goes into the first group, the second fixture in the next group, the third fixture in the first group, and so on until there are no more fixtures.
The Next and Prev can be used to change the MAtricks X values. Values 0 and 1 are used to select the two groups.