Welcome back to the Wefugees and thank you for reaching out to us.
This website published by the "Flüchtlingsrat Baden-Württemberg" (Refugee Council) gives a quite good overview on deportation and voluntary return regulations (it is in German though).
They are basically referring to 4 possible constellations in which your obligation to leave the country ("Ausreisepflicht") will get executable/enforceable:
1.) There hasn't been lodged any appeal against the rejecting "Bescheid" of the BAMF (in time) and the deadline of the departure is over ("Ausreisefrist").
2.) The urgent/emergency appeal ("Eilantrag") in order to achieve a suspensive effect ("Aufschiebende Wirkung") got rejected by the court.
3.) An appeal, including a prior suspensive effect, got rejected by the court and there are no appealing options/legal remedies left.
4.) A person hasn't made any use of a potential right/option to get a residence permit or legal stay. However, the obligation to leave will not be exectuable as long as the deadline for the voluntary departure isn't met.
The length of that period varies from 30 days for "simple" rejections to 1 week for "obviously unfounded" rejections or "inadmissable" rejections. Still, even if you don't leave the country within that period or didn't contact the immigration office to signal that you want to leave (in your case the ZAB) it is not a necessary consequence to get deported. The authorities definetely prefer that you opt for a voluntary return instead of a deportation. But the exact procedures and the attitude may also vary from region to region (immigration office to immigration office).
To give a quick summary: Officially the period they grant you to leave voluntarily as soon as one of the 4 above described constellations occur will be either 1 week or 30 days.
Am I right with my explanations dear @mbeon-Ruth or @mbe-on_Zsigó or is there anything you can add?
I hope this helps and all the best,