The second scholarship declaration attests that you have not been provided by an Erasmus Mundus Action 2 scholarship in the past.

According to the Erasmus Mundus Action 2 programme guide:

Neither European nor third-country students can benefit from a second scholarship for the same type of mobility under another project under the EMA2-STRAND1.

This rule does not apply to Staff candidates. Furthermore, staff candidates cannot benefit from more than one mobility activity within the same project.

You can find the template here:  Second_scholarship_declaration.