Yes, the pulse length of the discriminated START and STOP signals on the SYNC output is directly related to the input signals being above/below the threshold. The SYNC_1 output is a Fast-NIM type (ref. Fig. 3.5). The nominal current source is 28mA crresponding to 14mA into an external 50 Ohm resistor. But the exact value is not very accurate and tends to be a little higher. Typically there might be an overshoot to about -0.9V and a constant value of -0.8V into 50 Ohm.