Maybe someone else with better technical knowledge could chime in and give you a better answer but I found the same thing with Berger data for my 300 WSM
. Their max loads were the starting loads in one of my books. I just started at their max load and worked my way up towards the max listed in my book. I found best initial accuracy right at their max load but my velocities were almost 100 fps slower than they listed, a little tinkering around produced the velocities I was hoping for and great accuracy as well.
For the 22-250 loads they sent me, their data was a close to my usual books and ironically enough my best loads came right about their max load listed. I think you should be fine to start with their data and work up to your old load. Just remember there is no free lunch so if you start getting way higher velocities than you should before getting pressure signs, you are already pushing the pressure limits.
Also, make sure they sent you the data for the right bullet, that could cause some load discrepancies.