Positive pressure isolator leak test procedure

Can anyone guide me for how to perform the leak test for positive pressure isolator used in sterile area?

I can understand the formula mentioned in ISO 10648-2 for Pressure change method i.e.
hourly leak rate, Tf = 60/t X (pnt1/p1tn - 1)
t is the duration of the test in minutes,
p1 is the absolute pressure (ambient pressure minus under pressure) at the first reading in pascals
pn is the absolute pressure at the last reading in pascals
T1 is the temperature at the first reading in kelvins
Tn is the temperature at the last reading in kelvins
60 represents the 60 minutes in an hour

But for positive pressure what formula we can use?

Can anyone help me to understand this?
In ISO 10648-2, hourly leak rate formula is mentioned for Pressure change method.
In this pressure change method, it is written as “When the containment enclosure is at positive pressure , an equivalent method can be also used”.
So, my query is what method can we use for positive pressure isolator?