Slimes will not despawn

I'm trying to make a mechanic where if someone right clicks a slime of any size with an empty bottle it'll not only fill the bottle but also decrease the slime's size.
However, as shown below, this doesn't work when adding other else-if statements and will ALWAYS despawn the slimes regardless of sizing. Does anybody know what could be causing this issue?
I should also note; i've already tried changing the less than or equal to parameter on the last elseif statement but it still doesn't work.