Help internal memory filled when downloading an app

[cantorevan]

I downloaded for my phone "Potty Time" for my toddler and didn't realize that it required 33 MB. So when downloading, a message appeared that there's not enough memory and download would cease. However, my internal memory is not all filled up! I proceeded to empty caches and delete saved info from other programs, but I'm still stuck at 17.64 MB and want to delete the program info for "Potty Time" that's clogging my memory. How do I access it?

My phone is rooted and I have OI Folder Manager.

Thanks so much!