I suggest that it's made mandatory to write numbers in lyrics in words to improve readability & to make it easier to follow lyrics in languages one doesn't speak. To give an example, instead of
365 gün saňa garaşdym
one should write the lyrics as
Üç ýüz altmyş bäş gün saňa garaşdym
so someone who doesn't necessarily speak Turkmen can also follow the text.