Canon SLR cameras have a "metering timer" in the menu. What is this for?

The "metering timer" in the menu of Canon SLR camera is used to lock the exposure value to prevent the exposure value from changing when the composition is reshaped. For example, if you want to take a middle shot of a character (not a close-up of the face), first use the lens to enlarge the face of the subject to measure light, and then press the key of "Metering Timer" (marked with *), and the locking time is the time you choose. Then re-compose the characters and take photos. The choice of time is based on the time when you need to compose again. If you can finish repainting and taking photos within 16-30 seconds, of course, you should choose 30 seconds.