Hi
No buttons available from backend, but you can change values editing this file
/templates/ja_teline_v/less/variables.less
// 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);
After you changed px values for your desired screen size you will need to click on button compile less
Regards