DVD+RW 4.7GB only able to record 2.2GB, why???

Details, man, details... what kind of system? What brand of DVD-R? What speed are you trying to write at? Which program are you using to burn? What is the exact error message, if any? Please provide some details you think might help us diagnose the situation.

It's nearly impossible to even begin to troubleshoot without any kind of information other than "DVD is not burning correctly."