This gist is used in the tutorial https://www.vijayan.in/how-to-create-custom-table-list-in-wordpress-admin-page

column_default.php

<?php
...
	/**
	 * The Default columns
	 *
	 * @param  array  $item        The Item being displayed.
	 * @param  string $column_name The column we're currently in.
	 * @return string              The Content to display
	 */
	public function column_default( $item, $column_name ) {
		$result = '';
		switch ( $column_name ) {
			case 'date':
				$t_time    = get_the_time( 'Y/m/d g:i:s a', $item['id'] );
				$time      = get_post_timestamp( $item['id'] );
				$time_diff = time() - $time;

				if ( $time && $time_diff > 0 && $time_diff < DAY_IN_SECONDS ) {
					/* translators: %s: Human-readable time difference. */
					$h_time = sprintf( __( '%s ago', 'admin-table-tut' ), human_time_diff( $time ) );
				} else {
					$h_time = get_the_time( 'Y/m/d', $item['id'] );
				}

				$result = '<span title="' . $t_time . '">' . apply_filters( 'post_date_column_time', $h_time, $item['id'], 'date', 'list' ) . '</span>';
				break;

			case 'author':
				$result = $item['author'];
				break;

			case 'type':
				$result = $item['type'];
				break;
		}

		return $result;
	}
...