The field cash_point_closing_export_id corresponds to the field Z_NR in the official DSFinV-K documentation and is described as follows:
The cash register closing is created for a cash register once or multiple times a day;
it can also be created for more than one calendar day. Each cash register has a “Z_NR”,
a cash register closing number. This number is ascending and consecutive and cannot
be reset.
Useful examples and descriptions of the different fields and business cases are given in the DSFinV-K documents of the Federal Central Tax Office (Bundeszentralamt für Steuern):
DSFinV-K 2.3, (new version) (EN)
DSFinV-K 2.3, Stand März 2022 (DE).