It's common to get sudden requests for help when you are in the middle of something. This method is a great way to (temporarily) hold off the request. First, you let the person know it's not a good time as you are doing something. Secondly, you make known your desire to help by suggesting another time (at your convenience). This way, the person doesn't feel blown off.
我们经常在很忙碌的时候接到突如其来的求助，那么这句话就可以起到很好的暂时性推辞的作用。首先，你让对方知道现在你正忙，时间不合适；其次，通过提出再次联系的时间让对方知道你是想帮忙的，这样别人才不会感觉被冷落了。（*blow sb. off 突然对某人很冷淡）