Informal way to say, "What you said is true; the rumor or the news is true." * /"I am told you're leaving our firm for Japan," Fred said to Tom. "That's about the size of it," Tom replied with a grin./
THAT'S ABOUT THE SIZE OF IT!
Meaning of THAT'S ABOUT THE SIZE OF IT! in English
Dictionary of English idioms . Словарь английских идиом. 2012