BUDS is it worth having

If it was reading  Low, You need to go down.  
If it WAS at 680; Try 350.  
The system might be scaling by 10 internally to keep the numbers friendly.
3 digits are more than enough to get calibrated to better than 1%.
Flow meters are not accurate to the 1% level under real world conditions.

Took the dongle and laptop for an airplane ride, recorded data at several throttle setting . A typical test was  as follows;

                           throttle percent- 95, Rpm- 5460, Map-  24.8. On BUDS fuel page; A fuel flow -213.5 g/min, B fuel flow- 213.3 g/min, 

                           On EFIS (Advanced 5600), fuel flow reads 2.3 GAL per Hr

Because A channel controls half of the injectors and B channel the other half, I wonder if A and B have to be added in the EFIS?   And if the EFIS

were only reading one channel perhaps that could explain the issure that the EFIS is showing about half of what the CAN busss is reporting?

Changing the K  factor has no effect on the EFIS reading. I await your comments.

Interesting. I did a grount runup at 3300 rpm. I then did the endine pre-takeoff  lane tests and found that when lane B is turned off the fuel flow doubles. So it seems that the EFIS is only using the A channel fuel flow output from the CAN buss.. My 5600 is an older one, (2 December 2011)still using OS-1 operating system. I will contact Advanced for advice.