Gallery (grid_lightbox) Width

Hi, I have read every forum posting regarding gallery size issues and nothing has solved my problem.

I created a new page where a grid lightbox gallery is to go.

But when I create a gallery and insert it, it is too wide for the page (I'm using a template based on the Default Theme).

I've followed instructions from other posts and added this line into properties.php - resize proportional : array('w' => 500, 'h' => 300,
and added this line to properties.php - resize cropped : array('w' => 120, 'h' => 130),

I've changed line 14 in grid_lightbox/index.php to :
$gallery = get_gallery(get_mediarss_url('gallery=' . $pg_id . '&thumb=120c&full=500p'));

And then uploaded the changed properties.php and index.php

I've tried refreshing the picture size by updating the watermark - but nothing changed.
So I created a new gallery, but still nothing has changed.
The gallery is the same size, and still too wide for the page.

Can you assist me please?