Please post your read only link.
Everything looks fine for me. 15px is the padding amount.
The -15px that looks good in author mode, is not displaying correctly in preview mode. I’ve highlighted the areas in red. The -10px is overriding the -15px.
This is the exact same problem that @gautamlakum had.
Ah, now I remember. You have to add another class to the Columns
main class and modify margins there. Probably a bug.