Dual entry visa with one being < 72 hours

I have an itinerary looks like the following
Toronto - Beijing (60 hours) - Tokyo - Beijing (7 days) - Toronto

Should I be applying for a dual entry type or a single entry?

The first part should be fine, but how does the issuing process works? If they see I have one already, will they stamp that instead of giving me a 72 hour free?

THanks