refused to drive truck sat as only had 4.5hrs driving left and job takes 7hrs driving.
i used a digi for 1st time 13nov at 17.00 appx, so i think i can drive for 90 hrs up till 17.00 ,27th nov, is that right 
t.o are saying im wrong as digi driving time is done on a rolling system [ dont understand that ]so even though i think ive only got 4.5hrs left ive got enough hrs left to do 7hrs driving on sat, but surely that would give me
85.5hrs plus 7hrs = 92.5hrs
i find the digis easy to use[ dont laugh 
] but this driving time with them is doing my head in, according to our t.o i can just about drive 24/7, but there not going to be there if it all goes ■■■■ up.HELP 
The fortnightly driving limit of 90 hours is calculated over two fixed weeks, no surprises there. The fixed week begins at 00:00 Monday and runs until 24:00 Sunday, this means that for period beginning 00:00 hours on Monday the13th November you can do 90 hours total driving between then and 24:00 on Sunday the 26th November. This is the same for digi tachos or analogue, there is no difference in the rules for different types of tacho head as regards this. It is done on a sort of rolling system in as much as week one and two are added together to reach the fortnightly total then when week 3 begins, week one is discarded and week two and three form the new fortnightly calculation. Week four begins and week two bites the dust etc. etc… Each new week begins as you pass midnight Sunday/Monday.
If you were doing a shift that started on a Sunday evening and finished on a Monday morning, and were getting close to the 90 hour limit, as long as you don’t exceed the 90 hours before midnight you can drive further hours after midnight. You enter a new fixed week then and the fortnightly calculation, along with the number of 9 hour rest periods and 10 hour driving days is reset at this point.
Given some of your questions regarding what your traffic office are telling you, it seems they are in serious need of driver’s hours training as they don’t appear to have much of a clu.