Help changing my music meme app from 15 second clips to 30 second clips.

I paid to get a music app made, which lets you create music memes. I spent alot of money and could not continue development of the app. One of the biggest problems I want help with is changing the amount of time from each clip you create using my app from 15 seconds to 30 seconds. I have the app coding and I do not know where to look. Can someone please help me?