What do the numbers on the tiles mean?

It should be the quality of the tiles, and the master's technique should not be so bad.

You can stick two bricks together face to face and have a look.

If a brick is flat, then two bricks will stick together. You'd better try on more pieces. If there is no gap, that is the skill of the master!

As for the figures behind, what doesn't affect you is the slogan in the factory!