TMdict

There are two main ending routes in CCC.
The flags you’ve triggered are tallied when you enter the seventh round.
If you’ve seen more Sakura related events, you will be headed for the true end.
If you’ve ignored Sakura and focused on your Servant, you will be headed for a Servant end.
The title of the seventh chapter is different depending on the route you’ve entered, so you can tell at a glance which route you are on.
…However, just because you’ve entered the true end route it doesn’t mean it’s impossible to reach a Servant end.
When on the true end route, when you open the last door you will be presented with a variety of choices which will affect which route you will ultimately head down, so don’t worry if you were aiming for a Servant end, it’s still possible.
The reason that the true end route is the “true” end is because it’s the route that reveals the truth behind the story that the protagonist doesn’t know yet. But it’s not only that. “Bidding farewell to your Servant” is an incredibly important part of the Fate franchise, and so the true end route was selected as the true ending because it has a proper Fate style conclusion.