pfSense

Issue is due to code in index.php:

<?php
    $columnWidth = (int) (12 / $numColumns);

    for ($currentColumnNumber = 1; $currentColumnNumber <= $numColumns; $currentColumnNumber++) {

        //if col$currentColumnNumber exists
        if (isset($widgetColumns['col'.$currentColumnNumber])) {
            echo '<div class="col-md-' . $columnWidth . '" id="widgets-col' . $currentColumnNumber . '">';
            $columnWidgets = $widgetColumns['col'.$currentColumnNumber];

this uses bootstrap's "col-md" classes, which use width percentages in steps of 1/12 (co-md-2 is 2/12, so 16.67%).
Since (int) 12/5 gives the result of "2", user has the impression that there are 6 evenly spaced columns but only 5 of them are used.

A workaround would be to create a new class with width of 20%, which doesn't exist inside bootstrap's "col-md" classes.