If you take a look at the AFM or AOM wichever, you will see charts that give you settings for various altitudes, temps. It will give IAS and maybe N1 and fuel flow. After you have spent all that time familiarizing yourself with the AFM chart data and carefully making the adjustments, the end result is .70 mach.
For some reason on the Hawker they did not spend much time refineing this data.
In other manufacturers jets you may find in the books that the lighter the plane gets the slower you can go wich is designed to keep best lift over drag, as time passes you must make adjustments. These companies have spent more time on the lift over drag number crunching.