Warning: A non-numeric value encountered

Health Check is throwing the following Warning on my site:

Warning: A non-numeric value encountered in /home/ms101admin/public_html/wp-content/plugins/health-check/includes/class-health-check-wp-cron.php on line 108

It doesn’t seem to be causing any issues, but I’d like to nip them in the bud if possible.

The page I need help with: [log in to see the link]