lbf.s is a unit of impulse, not force. Without knowing more your motor could be providing 2.25 pounds for one second, or 5.5 pounds for half a second, or 0.00225 pounds for 1000 seconds, or any other combination of force and time that multiplies to 2.25.

Force doesn’t even necessarily need to be constant, in which case the impulse, in lbf.s, would be the integral of thrust over time.