That is the same as too short history I think. The credit bureau the bank will pull your credit from depends on your location. Sometimes they pull more than 1 bureau as well. You can sign up for an account at credit.com. It's not the type of score banks use ro the bureau that specific bank pulls but it will tell you credit age/inquries etc so you have an idea.
I forgot to mention this to PointsLife1 yesterday. In the US, it is quite common to call a reconsideration line and ask them to take a second look at your application. (if it's not something like 5/24 rule) You might get lucky. If they still decline, at least you can ask for more info like when you should apply again. You can google Reconsideration Line and read about it, plenty of info available. When I applied for Chase Cards, I only called their recon line. For Citi personal cards, 1-800-695-5171.
From my research, Citi and Chase (and other banks) like to see at least 1 year history. However, the data points show that people with less than a year history can get approved as well (maybe a little more difficult).