Max time/unit for Proecuement Activitiy

Dear Sir ,

I have Procurement Activity od is 15 days and cal.5d/week

i have assign a resource ,( Procurement Engr.) he will work only for 2 hr/d for 15 days,

in Resource tab Bugeted Unit is showing 24 while it should be 30

Max time/unit * od 2 * 15 = 30 Hr.

Could you please advise where i am wrong.

Thanks