To better isolate the issue, you might want to delete and re-create the current check and see if it's still recording 2 numbers ahead. Otherwise, we have to perform basic troubleshooting steps. We can start by accessing QuickBooks Online in a private browser.
Here's how to open a private window in different browsers:
Google Chrome: press Ctrl + Shift + N.
Mozilla Firefox: press Ctrl + Shift + P.
Internet Explorer: press Ctrl + Shift + P.
Safari: press Command + Shift + N.
If you're able to record the correct check number, let's open your account using the original browser and clear the browser's cache. You may also try accessing your account using another supported browser. You may also try accessing your account using another supported browser.
I'd be happy to provide you this article to help guide you in printing your checks in the future: How to print checks.
You can stay connected with me by adding a reply below if you need additional help with QuickBooks Online.