Why doesn't Masonry js work for blocks, one=40%, second=60%?

Question

JavaScript

Good day!
Please tell me about Masonry js, the task is to arrange the blocks in 2 columns, 1 = 40%, 2 = 60%, but for some reason they do not stand next to each other. If I put the first block 20%, then everything becomes, I don’t understand why.
Example

Answer 1

Have you tried it without a border? =) It still takes 2 pixels, and you have a clear width of 100%. Those. Or remove the bodred or reduce the width by at least 1%

Answer 2

https://jsfiddle.net/eho3jgtg/2/