I designed the SM2100 and EZ-1 integrators for nuArc and am familiar with some of their lower-end integrators.
It is customary to initially have the integrator work at 1unit = 1second. The integrator and sensor are designed for optimum performance at this calibration. If the unit is counting too fast the pre-amplifier may be saturating - too much light is getting to the photocell and the integrator can't handle the signal.
If you set the unit to 1:1 with a new lamp it is easier to monitor the fall off in light output as the lamp ages. When it slows to 1/2 speed it is a good idea to replace the lamp.