Admin-ajax returns a 0

I am trying to write a simple ajax call that grabs the value of an input on blur and returns it. The ajax call is in a folder called ‘scripts’ in my themes directory and the function is in functions.php. My code is as follows:

$(document).ready(function(){
	$("#trading_card_amount").blur(function(){
	var cardAmt = $(this).val();
	$.ajax({
		type: 'POST',
		url: '/../../../../wp-admin/admin-ajax.php',
		data: {
			action: 'populate_qualified_cards',
			cardAmt: cardAmt,
		},
		success: function(data){
			console.log(data);
		},
		error: function(){
			console.log('error');
		}
	});
});

and in functions.php i have:

function populate_qualified_cards(){
    $amt = $_POST['cardAmt'];
    echo $amt;
    die();
}
add_action( 'wp_ajax_nopriv_populate_qualified_cards', 'populate_qualified_cards' );
add_action( 'wp_ajax_populate_qualified_cards', 'populate_qualified_cards' );

Any ideas why I only get a zero in the console log? Help please!!!!!