problem setting the width for the elements

hi!
I have created a grid to be the landing page to my blog using the drag n drop, where every piece of the grid will be a blog post, showing 5 posts in 3 columns:
– Column 1: post 1 and post 2,
– Column 2: post 3,
– Column 3: post 4 and post 5.
The default dimensions are 150×150, but i need them to be wider.

I thought that, by changing widgets base width & widgets base height, would be able to change the width of the pieces in the grid, but something weird happens.

If i place a bigger width, like 304px, the drag-n-drop options does not allow me to have more that one column anymore, nevertheless (with width 304px) i still have 2 columns displayed.

There is something that i’m missing or sth like that, because this is strange :S

could you help please?
thanks in advance for your time, this is the page in my web which is meant to be a grid blog: https://www.iversoncru.com/blog/

https://www.ads-software.com/extend/plugins/cbach-wp-gridster/