Need help to Understand KUSTO Scan operator

Can someone please explain how the output is prepared from this query. Not able to under why records are repeated in the output.

let tbl = datatable(Ts: timespan, nodeState:string) 
[ 0m, "Ready", 
  1m, "Ready", 
  2m, "Ready", 
  3m, "Ready", 
  4m, "Ready", 
  5m, "Ready", 
  6m, "Ready", 
  7m, "Ready", 
  8m, "Ready", 
  9m, "HumanInvestigate" ];
let b = tbl 
|order by Ts asc 
|scan with_match_id = mid declare (steps:string ) with ( 
step s1 output = all: nodeState =="Ready" => steps="s1"; 
step s2: true => steps="s2"; 
step s3 output =all : nodeState == "HumanInvestigate" => steps="s3"; );