Vuetify: [Documentation] XS Breakpoint for v-col

[wonderf]

Environment

Browsers: Chrome 76.0.3809.100
OS: Windows 10

Steps to reproduce

see at API window

Expected Behavior

Write something to use xs breakpoint.

Actual Behavior

In v-card doc I am find magic combination v-bind="{ [xs${card.flex}]: true }"

Reproduction Link

https://vuetifyjs.com/en/components/grids

[squalsoft]

xs = cols
xs3 (xs="3") will be
<v-col cols="3">

[MajesticPotatoe]

as stated above, when no breakpoints are provided, xs is assumed, and cols is essentially replaces this.
related: #9233