If a “SPRING TENSION” command is specified and the spring is stretched along the positive global direction (due to a positive global deflection of the node to which the spring is attached), then the spring is identified to be in tension and you will have the spring support reaction as negative by the virtue of it being opposite to the displacement. If however, the displacement is negative, the spring is identified to be in compression and the spring will be switched off from the model.
If a “SPRING COMPRESSION” is specified and the spring is compressed along the negative direction of the global axis (due to negative global deflection of the node to which the spring is attached), the spring is identified to be in compression and you will have the spring support reaction as positive by the virtue of it being opposite to the nodal displacement in the negative direction. If the displacement is positive, the spring will be identified to be in tension and will be switched off.
In the following figure, consider a compression only spring support is specified in Global X direction. Due to the applied load in negative X direction, the support node (node 9) will displace in the negative global X direction. So the spring support will be under compression and the support reaction in Global X direction is positive. The support will therefore be active in this case. Had it been a SPRING TENSION type support, it would have got deactivated.