Using -l and -ti

[Eywayä Kelku]

Kaltxì!

I was just reading 'easy guide to suffixes, prefixes and infixes, and I'm a bit stuck on something.
You know that there is -l and -ìl used to show that it is the subject doing the action to the other noun. When do you use -l and when do you use -ìl if the both mean the same thing?

[Hawnuyu atxen]

Kaltxì!

It depends on whether the word ends in a vowel (-l), or a consonant (-ìl).
Same for all the inflections, what have two allomorphs (-ru/-r and -ur... -ti/-t and -it... etc.)

[Eywayä Kelku]

Oh! Irayo! I get it now.

[Hawnuyu atxen]

Glad i could help

Oel ngaru srungit tamìng a fì'u oeru prrte' lu