Overlapping in Demand assignment to resource in MRS

Dear Experts ,

    Need help on Demand assignment to resource in MRS (Ver 10) .

Say a resource R1 works from 6 am to 2 pm (8 hrs). Hence ideally, the max work that can be loaded to this resource can't be exceeded beyond 8 hrs. But practically I can assign any number of demands to this Resource., without any warning/Error message.

Say

Order 1-- > Demand 1 from 6 to 10 (4 hrs)

Order 2-- > Demand 2 from 6 to 14 (8 hrs)

Order 3-- > Demand 3 from 8 to 10 (2 Hrs)

Practically It's not possible to assign more than 8 Hrs work to this resource...Also the next demand should be started after  finishing of first demand. Then why system is allowing me to assign demands more than 8 hrs , with overlapping (more than one demand ,starting from 6 am)?? Am I missing any setting here..?

Please help to find the issue..

Thanks

Denny