Alerting math with negative numbers

I have the following alert rule setup and best as I can tell it is firing on ports that have a negative value that is between the High and low values. Am I missing something in my logic?

sensors.sensor_current < "%sensors.sensor_limit_low" AND sensors.sensor_current != 0 AND macros.device_up = 1 AND sensors.sensor_descr != "Cellular 3G RSSI"

#1: sysObjectID => '.1.3.6.1.4.1.2636.1.1.1.2.134', sysDescr => 'NES1-RTR1', sensor_id => '1578', sensor_oid => '.1.3.6.1.4.1.2636.3.60.1.1.1.1.5.518', sensor_descr => 'ge-0/0/6 Rx Power'
#2: sysObjectID => '.1.3.6.1.4.1.2636.1.1.1.2.134', sysDescr => 'NES1-RTR1', sensor_id => '1579', sensor_oid => '.1.3.6.1.4.1.2636.3.60.1.1.1.1.7.518', sensor_descr => 'ge-0/0/6 Tx Power'