Ever noticed this too:
12,000 and 10,002 - Both are "Elfu kumi na mbili"
11,000 and 10,001 - "Elfu kumi na moja"
15,000 and 15,005 - "Elfu kumi na tano"
.......etc. You can add as many as possible. Seems counting became a problem for the swahili mathematicians regarding digits beyond 1,000. lol...