Interpreting the Results
Rate: This number represents how many seconds the watch will gain/lose in a day. A really high/low number could mean that the watch needs service or regulation.
Amplitude: Amplitude measures of how far in degrees the balance wheel is rotating back and forth. The goal of a watch movement is to minimize the amount of friction so that the most power is being transferred from the mainspring. A low amplitude (relative to the normal for a movement) indicates a higher level of friction and tells you that the watch needs to be serviced.
Beat Error: The beat error is the time difference between the ‘tick’ and the ‘tock’ of the movement. Ideally the balance wheel should swing exactly as far clockwise as it does counter-clockwise. A larger number, more than 0.4ms, could indicate a poorly regulated watch and anything more than 0.8ms really could indicate a problem with the balance.
If you're a watch nerd like me and you want to do a deep dive of this subject, check out this wonderful post by Beyond the Dial.