When dealing with multiple matrix jobs it would be good if the following sequence:
a) Start JobA (with priority # such that anything else is more important) that is a matrix of 10.
b) JobA-Part1 starts (JobA-Part2 - JobA-Part10 are in the queue)
c) Start JobB (with highest priority) that is a matrix of 10

Has the order of:
1) JobA-Part1 finishes
2) JobB-Part2 starts, finishes
... JobB-Part10 starts, finishes
3) JobA-Part2 starts, finishes
... JobA-Part10 starts, finishes.