What do the #s on the bottom of the Metropolitan Face of my Apple Watch 9 mean?

The first number is for Calories (outer ring (Red)).

The second number is for Exercise (middle ring (Green)).

The third number is for Stand (inner ring (Blue)).

Track daily activity with Apple Watch - Apple Support

We'd need a picture or screenshot to know what complications you have setup.

I just lifted this from Apple to explain their sample photo.

The yellow circles at the bottom of this watch:

Lower left = Timer

Lower right = Fitness (Activity) rings

Red circles at top are two more complications.

You can get excellent details of all of the different faces and the complications that are available for each:

Apple Watch faces and their features - Apple Support

You can learn how to set up your faces here:

Customize the watch face - Apple Support