Main.css seem wrong

I found this issue when i use attribute [col-3] and box width not seem like what i expect.
So i inspect code and found that [col-3] got width 42.85714% instead of 25%
This is the code in main.css

Capture

From picture above col-7 got 100% width which mean 1 row have 7 columns? not 12?

But when I go find code in ionic.scss in node_module nothing wrong with it

I’ve tried delete node_module and www folder then reinstall it and build again.
The result still same as before. For now i fix it by copy code in ionic.scss and place it in app.scss