I worked hard to get mine and my kids telephone numbers under 70, it's half hell otherwise.

Say 92 87 78 97:

4 20 2 4 20 7 60 10 8 4 20 10 7

Easy peasy right 😁, well you do get the hang of it but it's easy to mess up somewhere in the middle, especially if you do have a real 20, 10, 4 and so on.