Calculate present and next value

try with this.

let
    rr = Table.Group(yourTab, {"Group"}, {{"Breaks", each brksGroup(_), type table}}),
    tbe = Table.ExpandTableColumn(rr, "Breaks", {"List.Breaks"}, {"List.Breaks"})
in
    tbe

where, brkGroup is the following code.

let
    breakTab=(tab as table) =>
let
 tabSorted=Table.Sort(tab,{"Start"}),
 breakList=List.Accumulate(List.Numbers(1,Table.RowCount(tabSorted)-1), {},(s,c)=>s&{tabSorted[Start]{c}-tabSorted[End]{c-1}}) 
in
Table.FromColumns({breakList},{"List.Breaks"})
in
    breakTab

PS

the code intends to produce a break list, in case of multiple interruptions