AF-0099

Der angegebene Wert ist ungültig. Die Gesamtbruttosumme der Rechnung (…) muss größer oder gleich 0 sein.

In English The invoice total must be zero or more.

error: the document is invalid

What the rule checks

As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.