Nachbarzehner
... German for neighbouring tens (externer Link)
"Nachbarzehner" are dealt with in primary school. "Nachbar" means neighbour. "Zehner" here are all numbers divisbile by ten. Here are some "Zehner": 0, 10, 20, 30, 40 etc.
Each number has to such "Zehner" next to it: one "Zehner" to the left and another "Zehner" to the right. They are the "Nachbarzehner".
The Nachbarzehner of 2 are: 0 and 10.
The Nachbarzehner of 13 are: 10 and 10.
The Nachbarzehner of 30 are: 20 and 40.
The Nachbarzehner of 149 are: 140 and 150.