Planning small activities

If you plan very small activities, maybe you should change unit for work (in global parameters) to set it ti hours.
Then you can manage fractions of hours (0,1 h).

But is it really reasonable to manage such small tasks ?
Maybe you'll spend more time managing them than treating them
IMO, tasks should not be spit to less that 1 day activitiy, and best size is about 5-10 days...