How do I connect my stadia Profile on the site and app ?
For your profile to work properly, it will need you to login and create an account with the correct username same as Stadia. Founders don't need to add #0000 but if you are not a founder and there are multiple users with your user name adding your full username is required. Using the same e-mail address is not necessary but it's the best way to precisely find your account.
Do I need to login ?
Not necessarily. I want to make every feature of the app available to everyone but for tracking your games, comments and stats information, it is required. But I do appreciate you do login at least once to create a profile because it helps tracking more games, achievements and time played making the information more accurate.
The game leaderboard is only tracked for the players currently in the App. Warning : In case of games with secret achievements the completion time may be wrong if the last achievement completed is secret.
How long does it take for my profile to update ?
After finding your correct profile on Stadia, the website starts updating at midnight UK time (00:00:00 GMT +01:00). After finishing the updating everyone games and achievements it will count the total for each user and globals to build a correct Leaderboard and Game Stats
Missing Games and Achievements
You will need to play at least once a game so it shows in the website and Secret achievements are only tracked if I (Endeavour#6399) already completed those otherwise it won't be able to track the completion times on those although this won't affect the overall count of completed achievements. Same works the other way around, in case of free days or refunded games this will show exactly how Stadia displays it.
The score in the leaderboard is currently calculated by the number of achievements you completed plus the number of games you completed. Each achievement is worth 1 point and each game is worth 10 points.