Bekanntgabe
The day a decision counts as having reached you.
For decisions sent by post, the fourth day after posting counts as the day of notification (§ 41 Abs. 2 VwVfG, § 122 Abs. 2 Nr. 1 AO, § 37 Abs. 2 SGB X). The deadline runs from then. If the letter demonstrably arrived later, the later day counts.
How it appears in the letter
»Der Bescheid gilt am vierten Tag nach Aufgabe zur Post als bekannt gegeben.«