Problem

In Print Organizer while creating Print Styles, I am able to set more than one print style as the "Default". Is this correct? 

Solution

Yes, you are allowed to have more than one "Default" Print Style and here are the rules on how they are applied:

To ensure that you have an opportunity to override any print style default properties, the product always processes print
styles in a particular order.

Default print styles are always applied first when print definitions are added to Print Organizer or when the Print dialog
is opened. If you have multiple default print styles, they are applied in the order they are read. Mutually exclusive
properties that may appear in subsequent default print styles override the same properties that appear in previous default
print styles. Print styles are read in the order they were created within a single file, and in the order of placement
within the configured DGN libraries.

If both a default print style and a print style that is assigned to a printer driver configuration file exist, duplicate
or mutually exclusive properties in the print style assigned to a printer driver configuration file override those in the
default print style.

Any properties specified by manually applying a print style, always override any duplicate or mutually exclusive properties
in a default print style or print style assigned to a printer driver configuration file.

Any properties manually specified in the Print dialog or in Print Organizer after a print style has been applied, always
override any duplicate or mutually exclusive properties in the applied print style.