R.I.Y.B.A.

The matchup grid shows which teams have been scheduled against each other in pool play rounds and during the first round (and possibly second round - dependent on whether or not one team had a bye) of bracket tournament formats.
 

The scheduler will use this to avoid pairing teams that have already played each other multiple times in either the pool play rounds or first round of a bracket tournament.
 

In a bracket tournament format, only a team's 1st game (and 2nd game if the 2nd game is against a team that had a first-round bye) are included.
 

In a pool play tournament format, only a team's games played during the pool play round are included.
 

Forfeited games do not count in the matchup grid.
 

These are the primary factors when pairing teams for scheduling.  Other factors include blackout times and the number of available teams participating in a particular tournament.