Not 100% sure about this, but this is what I think/guess. 
Your AC might have two stage cooling (lucky you), so it will indicate this on the thermostat when it's active.
See :
Thermostat: http://www.centralite.com/index.php/products/azela/azela-thermostat
2 Stage cooling: http://www.lennox.com/help/faqs/two-stage-cooling
Hope this helps