Change volume-steps in Ubuntu 18.10? (Gnome Shell)

Question

On Ubuntu 18.10, on my laptop (Lenovo W530), there are 2 ways to easily change the volume:

• + / - buttons on the keyboard:
  
• Scroll wheel Up/Down on the speaker icon with the mouse:
  

Using the + / - buttons has 17 steps from min to max.

Using the scroll wheel has 50 steps from min to max and I find it too low.

My question is: how do we change either step size?

This may look like a duplicate of how-can-i-make-the-volume-change-in-smaller-increments but it's not: this question is about Ubuntu 18.10 running Gnome Shell, not Unity.