create pre-filter with multilevelselect

I'm using the multilevelselect for country-state-city

I've read the documentation about the pre-filtereds links but still have some questions:

http://www.com/index.php

?option=com_cobalt

&task=records.filter

&item_id=12

&filter_name[0]=filter_type

&filter_val[0]=2

This only sets the type to 2, which is correct. The multilevelselect field has ID = 15 but i only want to filter by the first level... leaving the remaining 2 levels without selection.

First level of field has this values:

Portugal

Brasil

Angola

Moçambique

For this to be accomplished i would have to add:

&filter_name[0]=filter_k48f35c43525906b62b7e87eca10fd8b7

&filter_val[0]=Portugal

to filter by Portugal, i believe... but beeing a multilevelselect i believe it needs changes. Is this correct?