If this is an existing watch face before you mess with the face I’d make a backup (done via share face). I’ve lost customized faces in the past after an update and not realizing it. Your image may be a custom face from the manufacturer of the monitor. The x-large face another post mentioned is the only one with a display of time similar to your posted image.

It seems to me that the monitor’s manufacturer should provide a watch face to download. Below is snippet from the web describing glucose monitoring.

“The exact process of setting up the continuous glucose monitor so that it delivers alerts to an Apple Watch will vary depending on the product. In the broadest sense, you’ll likely need to install the product’s companion app on your iPhone and adjust its settings so that you get the kinds of alerts you want, such as emergency alerts about dangerous blood sugar fluctuations. Because it is critical to set up the device properly, you should carefully read the instructions included with the product and get in touch with the manufacturer’s customer support team with any specific questions and for help setting up the system if necessary. The instructions used for setting up one product may not be applicable to a different product.”