Yeah, this confused me as well

I was about to ask the same exact question! Please help!

Look at this.

After 10,000 it is common to let the number precede elfu: kumi elfu, ten thousand. By doing so, confusion is avoided. Note that: kumi na moja elfu is 11,000, while kumi elfu na moja is 10,001, and elfu moja kumi na moja is 1,011 

There is no such number as "elfu kumi na moja"; this would not be understood. 

A variation of mia tisa is sometimes heard, tisa mia: elfu moja tisa mia themanini na nane, 1988. 

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In compound numbers, only the units, or the tens when no unit follows,are preceded by NA: kumi na tano 15 thelathini na tisa 39mia mbili sitini na nne 264 mia mbili na sitini 260 kumi elfu mia tano sabini na mbili 10,572 kumi elfu mia tano na sabini10,570 laki moja arobaini elfu mia nne na kumi 140,410 laki tatu sitini elfu mia tano sitini na moja 360,561 

here is the link to this website https://kamusi.org/content/numbers