How to make my app tablet friendly?

I want to comply with this google play optimization tip, but I have no idea what more I have to do.

“Your layout should make use of the available space on tablets”

53903-clipboard01_design+for+tablets.png

The graphics elements of my game automatically are adjusted to any variation of screen size. On my tests I always use all the screen size of any display.

This is my app: https://play.google.com/store/apps/details?id=com.denysalmaral.CrabbyBall
Bluprints only project.