Negative values caused by ReWire
Usually unexpected negative value for big number is caused by overflow.
ReWire implementation is using 32bit integer pulses per quarter note to represent time value and the desired time may be too big to handle by using 32bit integer number.
We recommend using MIDI in your configuration for the best timecode match. You can find out how to implement MIDI on our website.
MTC uses the real timecode value and no worry about overflow.