BigTweet allows you to post 280 characters to twitter.
This is what my test posts looked like:
Testing BigTweet. BigTweet runs on the Amazon Elastic Compute Cloud (EC2). Amazon SimpleDB is used to store usernames and encrypted ...1/3138 characters
...passwords for users who wish to remain logged in at the end of a browser session - see the "Keep me logged in"checkbox used at ...2/3136 characters
...login. End of test. ...3/328 characters
That's a total of 302 CHARACTERS. Then you need to subtract the formatting characters that BigTweet enters for you. That means the leading "..." from 2 posts, and the trailing "...1/3", "...2/3", "...3/3" characters.
So that's (138 -6) + (136 - 9) + (29 - 9) = 279
Here's a look at the entry screen:
280 Characters is Not Two Twitter Posts
What's confusing is that even though BigTweet lets you post 280 characters, it breaks that down into 3 twitter posts.
Since twitter accepts 140 characters per post, you'd think that you'd be splitting your 280 character post into two posts.
A 280 character post ends up being split into three posts because of the extra characters that Big Tweet uses for formatting.