The behavior originally reported on this thread was changed in DAQmx 9.0 for position measurement tasks (both angular and linear). When reading scaled (DBL) data from a position task, the driver will typecast the raw count value to an I32 so it may represent negative numbers appropriately before applying the scale. A side-effect of this is that the scaled result will "roll-over" when the count hits 231, which will instead be interpreted as -231.
Edge count tasks currently still roll-over to the U32 value represented by the count register. For the discussion on the edge count behavior, see here.
Best Regards,
John Passiak