Something that came into my mind after the posting:
It is easy when you show the “Please consider buying Bitwarden Premium” message after the user has triggered some actions.
So read the list above as actions that the user has performed:
Number of Passwords is greater than 50 (or 100, 150, etc.)
Means after the user has added a new password and the total number of passwords is 50, 100, 150, etc.
This way the message is automatically shown only once (and when the user deletes password number 50 and adds a new one)
This way you have to understand the other entries in the list (add the text “After the user has…”):
User logged into the Bitwarden vault 100 (200, 300, etc) times
User logged into websites using Bitwarden 500 (1000, etc) times