scmJS docs

Modify Unit Shield Points

Sets the shields of the number of units of the type in the location to the percentage of their maximum.

Action 51 · Modify Unit Shield Points(Player, Unit, Percent, Count, Location);

Argument Takes Stored in the action
Player a player or group bytes 16–19
Unit a unit type, or one of the unit classes bytes 24–25
Percent a percentage, 0 to 100 bytes 20–23
Count a number of units, 1 to 255, or All (stored as 0) byte 27
Location a location (Anywhere is location 64) bytes 0–3
Modify Unit Shield Points("Current Player", "Protoss Zealot", 100, All, "Anywhere");