large-device-size - If the viewport is divided into 12 parts, this attribute indicates the relative space the container occupies on device-types larger than desktop. It is expressed as an integer from 1 through 12.
medium-device-size - If the viewport is divided into 12 parts, this attribute indicates the relative space the container occupies on device-types larger than tablet. It is expressed as an integer from 1 through 12.
Yet, in the Documentation tab it says:
If you specify the size and small-device-size attributes, the size attribute applies to small mobile phones, and the small-device-size applies to smart phones. The device sizing attributes are additive and apply to devices of the specified size and larger. For example, if you set medium-device-size=10 and don't set large-device-size, then the medium-device-size setting applies to tablets, desktops, and larger devices. You'd also have to set size to apply to devices smaller than tablets.
I find that contradictory. Can someone clarify if medium-device-size includes or does not include tablet? And similarly if small includes smart phones and if large includes desktops? I don't have devices to test and unfortunately can't test this in playground - but I did try by using Chrome developer tools to mock mobile on my desktop and was surprised to discover that the respective devices are excluded.. ie. small-device-size does not include smart phone. However, can't be sure if the simulated tabled/phone on Chrome worked or not. I imagine it will be same in Aura.