Pull Export Values from Checkboxes to Show in a Text Field

I'm having some issues with this script. I've used it successfully, but slightly different than this version.

I have confirmed each checkbox has a export value, but I can't get it to display the checkboxs' export value within the text field I have it assigned to.

I'm using this in the "custom calculation" section:

var ybl = this.getField("Length.Youth").value ;

var abl = this.getField("Length.Adult").value ;

if(ybl <= 31) {

    event.value = (ybl.value) ;

}

if(abl >= 32) {

    event.value = (abl.value) ;

}