Cannot set time

Was excited to try this so I could customize my own music into ringtones but cannot use this app. I can select songs but cannot set time. I choose start time, then go to end time, and app automatically resets to 1 minute. And it goes to the beginning of song. I am following time limits for each tones, but cannot figure out how to set the time. Have even deleted and reinstalled 2 times. Even went to app support page link offered in ITunes, but cannot read the foreign language. Forget this one.

SisterDee about 铃声大全 - 手机铃声制作设置助手