What is your problem with it?
It should only appear for a few seconds when the volume is changed.
If it lags on the screen for an extended time, that could be a sign that the device has too many things running- such as having multiple apps using accesibility service.
This can slow a device down so much that toast messages like that can linger for about 15 seconds.
If it only appears for 3-4 seconds, then it is normal and cannot be avoided.