SUPPORT affects the support costs of military units. The lower your score here, the more of your units you'll have to expend minerals to support.
-4, Each unit costs 2 to support; no free minerals for new base.
-3, Each unit costs 1 to support; no free minerals for new base.
-2, Support 1 unit free per base; no free minerals for new base.
-1, Support 1 unit free per base
0, Support 2 units free per base
1, Support 3 units free per base
2, Support 4 units free per base!
3, Support 4 units OR up to base size for free!!