Hi John,
As already mentioned, you should make sure that you only press the tempo buttons momentarily to change the tempo in increments of 1. Another option is to press one of the Tempo +/- buttons momentarily (so that the Tempo pop-up window appears) and then use the Data Dial to set the desired tempo. (On newer models, the tempo function is actually on the data dial by default (when the home display is shown), so you don't have to press a tempo button beforehand.)
Best regards,
Chris