Maximum pressure loss test: here's what we do...
Here's how we test pressure loss: We inflate the ball to the recommended pressure (meaning 0.8 bar).
72 hours later, the ball must not have lost more than 15% of its pressure, meaning approx. 0.1 bar (FIFA QUALITY PRO certification). The pressure after 72 hours must, therefore, be at approx. 0.7 bar.
This also means that it is quite normal for a ball to lose pressure after a few days.