Im looking at a Veltron Series 1500c low pressure differential sensor, connected to a 20,000 cfm air Trane handler. The sensor is reading 0.00024493" WC but it should be reading 0.16" WC. Is this a problem that can be corrected with the Zero dial?

This Veltron has the toggle switch on the bottom which, I think, allows you to zero the input pressure without disconnecting the pnenmatic lines. Should I flip the toggle, then turn the zero screw?