Translation:Elfu kumi na nane
I've been told intonation distinguishes them:
elfu kumi na nane = 18,000
elfu kumi, na nane = 1,008
elfu moja, (na) kumi na nane = 1,018
Apparently in Zanzibar, elfu often comes after, so they might be kumi na nane elfu and kumi elfu na nane respectively.
Here's how. This is what I was taught those several years ago back in Kindergarten. Normally people will say "elfu kumi na nane" to mean Eighteen thousand and such. But if you care for accuracy, this is the distinction;
Eighteen thousand - 18,000 - Kumi na nane elfu
Ten thousand and eight - 10,008 - Kumi elfu na nane
What changes is the position of the "elfu".