You may only have one topic per purpose (selling divines) every 4 hours and that includes new topics and bumped topics, it doesn't matter if you were to update quantities or prices.
So for example if you were selling 5 Ber runes and sold one, it doesn't mean you can create another topic straight away and list 4 Ber runes, you would have to wait 4 hours from the last reply of your previous topic in order to create another topic selling Ber runes.
Since you cannot edit topic titles, I suggest instead of featuring quantities and prices in your topic title you can feature them inside your first post instead and edit/update as you sell.
that i understand, what if i sell the 5 ber, and aquire 10 new ones. i would have to edit my previous post to - 10 ber in stock and wait for 4 hour bump?