The formula in this game is:

**a = b / 5 + 1**

Depending on what you find least confusing, either

1) There are two formulae, the first for white zones and a second one for other nations' zones, which would be:

**a = (b / 5 + 1) / 2**

2) In the formula, **a** doesn't count as the number of zones you have, but as something like "zone points". When you claim new zones, you count how many "zone points" you've spent, until you reach the value of **a**. White zones cost 1 "zone point", while other nations' zones cost 2 "zone points".