Hi,
Sorry for the late reply, you can check how its defined in the variables.less file, open the file and you would see the following code:
// Extra small screen / phone
// Note: Deprecated @screen-xs and @screen-phone as of v3.0.1
@screen-xs: 480px;
@screen-xs-min: @screen-xs;
@screen-phone: @screen-xs-min;
// Small screen / tablet
// Note: Deprecated @screen-sm and @screen-tablet as of v3.0.1
@screen-sm: 768px;
@screen-sm-min: @screen-sm;
@screen-tablet: @screen-sm-min;
// Medium screen / desktop
// Note: Deprecated @screen-md and @screen-desktop as of v3.0.1
@screen-md: 992px;
@screen-md-min: @screen-md;
@screen-desktop: @screen-md-min;
// Large screen / wide desktop
// Note: Deprecated @screen-lg and @screen-lg-desktop as of v3.0.1
@screen-lg: 1200px;
@screen-lg-min: @screen-lg;
@screen-lg-desktop: @screen-lg-min;
// So media queries don't overlap when required, provide a maximum
@screen-xs-max: (@screen-sm-min - 1);
@screen-sm-max: (@screen-md-min - 1);
@screen-md-max: (@screen-lg-min - 1);
// Grid system
// --------------------------------------------------
// Number of columns in the grid system
@grid-columns: 12;
// Padding, to be divided by two and applied to the left and right of all columns
@grid-gutter-width: 30px;
// Point at which the navbar stops collapsing
@grid-float-breakpoint: @screen-sm-min;
I recommend not to change the grid column as it is standard.
Regards.