Duration error - I entered days & it took it as hours.

I am new to P6 using P6v7.

I entered activities & their durations the normal way & added resources to the activities. It is showing like this: -

Original Duration Column as 20d [ fine as I entered 20 ]

Budgeted Units as 20h in Bottom Layout - Resources TAB. [ when i entered 20 as days, it took as hours]

This affected my Budgeted Total Cost Column, as my cost is taking the durations from the resources (in hrs.)

can anybody help, i guess some adjustment required in Preferences but i don t know where.