It's projected from the actual (then still unfinished) count but I think it uses some data from the exit polls to fill in the gap. So both?

We now have a preliminary official result. You can see it here: Saxony, Thuringia

@barsoap@lemm.ee has explained the basics of our electoral system pretty well: The first vote (Erststimme) is towards a candidate in a FPTP system to represent an electoral district and the second vote (Zweitstimme) for a party in a closed list proportional representative system. A party nominates a bunch of candidates and ranks them on a list. If they get enough votes to get a certain number of seats then those get filled first with candidates elected by Erststimme and then with candidates from the list starting at the top.

A party needs to win at least 5% of the Zweitstimme or win at least 3 seats using the Erststimme to be awarded any seats. This was done as a lesson from Weimar Germany where too many small parties made coalition building impossible which helped Hitlers rise to power.

But what if a party gets more seats via Erststimme than they should have? In that case we just start adding seats until the proportionality is maintained (those seats are referred to as Überhangs- und Ausgleichsmandate). That has lead to ballooning parliaments with our national parliament the Bundestag (small pronunciation guide: Bundes-tag not Bunde-stag - compound words can be tricky) being one of the biggest, right behind China. Recent reforms should curb that. We'll see next year how well they work.