The boilerplate comes with a standardized set of breakpoints, with the following specs:
|xxs||≥0||Normal mobile devices|
|xs||≥480||Large mobile devices or tiny tablets|
|md||≥1024||Large tablets or tiny desktops|
www/shared/styles/imports/custom-medias.css, you will find Custom Media Queries to target resolutions higher, higher or equal, lower and lower or equal for each breakpoint.
Here's an example: