Nid and cid are sometimes more than 13 digits

The add-on “link Cards Notes and Preview them in extra window” expects nid and cid numbers to be 13 digits long. It’s author says that is the standard length. But sometimes cloze notes are created with a 16 digit cid. I can’t pinpoint what triggers the problem but perhaps it is when a card has a lot of clozes, or multiple clozes with the same cloze number, or lots of data, like images. It still happens when I add a cloze note with all add-ons (including this one) disabled.
Are 16 digits also normal? In which case this add-on needs to be corrected to handle such cases?