julienmonnerie/kirby/config/sections/mixins/max.php

<?php

return [
	'props' => [
		/**
		 * Sets the maximum number of allowed entries in the section
		 */
		'max' => function (int|null $max = null) {
			return $max;
		}
	],
	'methods' => [
		'isFull' => function () {
			if ($this->max) {
				return $this->total >= $this->max;
			}

			return false;
		},
		'validateMax' => function () {
			if ($this->max && $this->total > $this->max) {
				return false;
			}

			return true;
		}
	]
];