What is your barrel length compared to what the load book list?
If yours is 20" verses theirs at 24", there is your missing 200fps.
The other thing as mentioned above, now you know your not getting what they did, instead of being happy your shooting sub MOA groups.
After you chase your tail trying to get what they got, then you will realize that the chrony while being a valuable tool in working up loads, can make your day less interesting if your simply looking for velocity which compares to factory or book listed loads.
I have two of them and I use them to look for shot to shot variations verses actual velocity when I am working up a load. About the only time I go by the actual velocity is when I am tuning up my bow. I know for a fact what it should shoot within 30fps, and with which arrows. With rifles or handguns, if I get in the ball park I am happy. If I am shooting sub MOA groups I am tickled to death.
Concentrate on the accuracy and once you have that, start shooting it out to 3-400yds, 5-800yds and so forth. Then you can figure your actual drops, and know for certain how well the load is actually shooting.
Mike / TX