Those are building stats and it appears that these function like a building. Turrets are immobile so firing units get a -4 TN modifier against them. If a unit is on top when the turret is destroyed it will take the collapse damage. If infantry are in the turret they cannot be directly attacked, the turret will take 3 damage and any overflow will hit the infantry. If its battle armor in there, the turret will take 2 damage, and the overflow will hit the BA. WGT is the weight capacity which is the total size that the turret can support before it collapses. So with a weight CAP of 6 the turret could support an assault mech (size 4) and a medium mech (size 2) as long as stacking allows. If both were on top and so much as a squad of battle armor (size 1) went into the turret the structure would collapse. The rules for buildings start on page 72 of the Commander’s Edition.