I've seen the misconception so many times now, so just to re-iterate
Your position in the Points Standings is completely irrelevant to getting into the Round 6 Top 24 race, this Top 24 race in particular is using Driver Rating as the primary matching parameter, not Championship Points. The 24 Drivers that are selected for the race will be the 24 highest Driver Rated players that sign up to the Top 24 timeslot, whilst also conforming to the 2 Manufacturer limit or the Country limit in your region. Championship Points carry absolutely zero weight in this particular Top 24's selection process.
How do you tell if you are one of the Top 24 Rated drivers? You can't, but if you think you might be eligible, I fully encourage you to sign up the timeslot anyway, You have absolutely nothing to lose by signing up irrespective. The game will politely kick you back to the Sport Mode menu and tell you that you didn't make it if you didn't get in, and will allow you to enter a following timeslot.