The social media network is also testing not counting "@" replies toward a tweet's character limit.
The graph below from Twitter explains the old structure and the new format for tweets:
Say more about what's happening! Rolling out now: photos, videos, GIFs, polls, and Quote Tweets no longer count toward your 140 characters. pic.twitter.com/I9pUC0NdZC— Twitter (@twitter) September 19, 2016