Bladder size doesn't always correlate with urgency either. I did a bit of brief reading on this awhile ago, and as best i can recall, the average "first warning" is at 150mL, and capacity can vary greatly, from 300 up to nearly 1000mL, which seems like an incredible amount. Even if your bladder can technically hold 700mL, you may "get desperate" by 500, or less even. Several have posted here in the past about surgery problems that damaged their bladder's "stretch sensors", causing them to get a desperate urge with only a very little amount present. (150mL etc) So, ymmv.
On the other hand, someone I knew had a problem with his prostate swelling and restricting his flow, and by the time he went to the ER (in agony) and they cath'd him, they had set up a bag for measuring output and he put 2.5L (yes really) into several bags over the course of the next 12 hrs. (they periodically closed the valve for awhile so his bladder could relax gradually) Hard to say how much of that was capacity and how much was his kidneys getting back to work after the pressure went down. Either way, high backpressure on the kidneys can cause permanent damage to them, which is why you'll get advice "not to hold it too long".