This is the second week of the event. The first having only 7 challenges.
This week gave us 10 challenges, meaning unless you did everything in the first two events, it was only awarded 17.
There are still 4 more events over the course of this season, so it should be reasonable to assume that getting the entirety of the event is still within the realm of possibility.
In week 6 I hope they can just make it so you can complete it all or bring it back in season 2 cause I have only completed 10 tires not even going to be able to complete it, they way they designed this event honestly makes me want to delete the game