Hello bornplaydie!
This is explained in a different post than the one you quoted:
Anicca, Dukkha, Anatta – Wrong Interpretations
At the top of that post:
“These three words with eight letters are: anicca, dukkha, anatta. (when written in Sinhala/Pāli: අනිච්ච දුක්ඛ අනත්ත but with last two letters in each term in the “old script” combined to become one, so the number of letters become 8 instead of 11. I was able to find only අනත්ථ for අනත්ත, but you can see how 4 letters become 3 there).”
If anyone can find the Sinhala word with three letters for අනිච්ච, please post it. There, the last two letters should be “combined” as in අනත්ත to අනත්ථ.