New field shows wrong values

[_Tuco_]

I need to create a new field which shows only the users that reached a specific landing page of a website, with data coming from GA4. This field is needed so I can use it further to perform some calculations with other fields. 

I tried the following expression to get the number of users: 
count(Page title = 'name of the page')

The problem is that this expression gives me a wrong number when I go to the GA4 and compare, and it's not a small difference. I tried also with page path and gets even worse. I think this expression would need to have some reference to users but i couldn't figure out, even after some time in ChatGPT or youtube... I would appreciate every help!