Don't worry lah. At first before enter BMT I 2.4km always
15minutes.
After BMT, within 12:20 already, just enough to pass.
Don't stress yourself too much, doubt many people train before
going in anyway. U just go for jogs at your own leisure pace, and
slowly build up speed. Within 1 month or so, u should find urself
able to jog for more than 20mins.