Problems with Boinc

There is some problem with down loads. I got down loads of 75 hrs single unit of work and the time to report was 6.12.07, where as download was done on the 16th of Jun, so it has to be completed 4 days before it was given.I think some thing needs seeing into to correct these errors. I would like small units of 4 to 8 hrs unit rather than 75 hrs unit, which i could never complete in time.