No, your understanding isn't quite correct. Many western central banks hold long dated bonds on their balance sheet which they are marking down due to increasing interest rates. Different central banks are dealing with this differently. In the US they are writing IOU s that essentially mean future surpluses will be used to pay back negative equity. The UK Treasury recently wired the BoE a large sum for much the same reason. Essentially, the bonds which were profitable during decreasing interest rates and resulted in central banks paying treasuries are now moving the opposite way.