I realised that the "Top 10 days ranked" statistics in the leaderboard only show consecutive days.
For example if you are ranked #10 5 days, then drop out for a day and then you get in the top 10 again for 3 days, then your score on the leaderboard is 5 days.
Is it meant to be like that?
Yes. This is by design(if you hover over the info icon, it should say this as well). This is to encourage players to stay on the ladder for longer periods. If you leave or go on vacation, your counter resets and you try again ;)