To remove media from the inputfield, hover your mouse over its thumb and click on its trash icon on the top left. A reddish border will be applied to the media thumb denoting that it has been marked for deletion. Save the page to remove the media from the inputfield.
To select all media in the inputfield in one go, double click on the trash icon of any of the media. All media in that inputfield will be marked for deletion. To select a range of media, use shift + click. First,select the first or last media you want in the range. Secondly, shift + click the trash icon of the last or first media respectively that you want in the range. All media in that range will be marked for deletion.
The above work whether you are in grid or table view.
Please note that this action only removes the media from the inputfield. It does not delete the media from your Media Manager Library.