Rules Question

So, I have a Land Raider shooting a Twin-Linked Lascannon(S9/AP2) at the side armor of a Leman Russ(13).

Roll, one hit (after TL reroll)

Roll wound? it's a 4.

9 + 4 = 13

So that's a Glancing Hit, correct?

Roll on the results table, 3.  Minus 2 for glance 1.

So instead of "Weapon Destroyed", it's a "Stun".

Is this correct?

Asking, because of a game I watched recently.  Whereas the owner of the Land Raider rolled the 4, and stated it was a Penetrating Hit, rolled a 3 and selected what weapon was destroyed.  I'm new to the game, and was a bit confused.

~rob