If you are using PlayScore 2 as an accompanist, you may not want the app to start playing until you are ready. This is the purpose of the Count-in feature. Count-in will tap out one or more measures before the music starts, giving you time to pick up your instrument.
Tap the Count-in icon 2nd from left at the bottom. Tap+/- to set the number of measures to be counted. If the music has a pick-up bar or anacrusis, Count-in will also tap the beats prior to the first notated beat.
While one or more measures of Count-in are set they will be played before the music starts wherever you tap in a score.