If you scroll back a while you will see my previous posts on this subject. Rate 1 is the “full-rate” reading and Rate4 is the 10 hour reduced rate. I think you are right that the T rate is a total (approx- as mine doesn’t perfectly match 1+4 either) The time is never quite correct as these meters no longer get an external time signal since the BBC stopped providing it! The clocks do not change to summer time so should be on roughly GMT year round. If you use any plug in timers it’s best to occasionally make sure that they are synched with the meter clock! Best of all with these meters ALL the power used during the 10hr slot is charged at the lower rate- so if you want to get the best deal that is the time to use energy hungry devices such as washing machine, dishwasher, dryer etc. Any storage heaters and hot water immersion heaters should be set up so that they can ONLY be supplied during the ten hour slot.