Tarmack
Rhetorical Porcupine
mine is 24% I hope it increases but I really don't know how!!
This is going to sound incredibly mean, so try to take it as constructive as I've not watched your material.
A low retention rate means one of two things. Either you have misled people into watching your videos who were looking for something else, or your videos found the right audience but weren't good enough for them to stick around to the end. 24% is not a good retention rate, so I'd have a good long look at my content were I in your shoes.
Barring those who mislead people, retention is almost always a video quality issue. Keeping people entertained throughout is how you keep them from clicking to some other shiny thing on the YouTube page.