Total Weekly Figure in trend graph

NewbieJono , Last 4 week

Measures 

Last 4 weeks =
var _max1 = maxx(allselected('Table'), 'Table'[date])
var _max = maxx(filter(all(date), date[date] = _max1), week[Rank])
return
CALCULATE(sum('Table'[Qty]), FILTER(ALL('Date'),'Date'[Week Rank]>=_max-4 && 'Date'[Week Rank]<=_max))

last 4 week based on today

4 Week today =
var _st = today() +-1*WEEKDAY(today(),2)+1 - 28
var _end =today()+ 7-1*WEEKDAY(today(),2)
return
CALCULATE(SUM(Sales[Sales Amount]),filter('Date','Date'[Date]>= _st && 'Date'[Date]<=_end )) //use all('Date') if need in filter

Columns you need in date table

new columns
Week Start date = 'Date'[Date]+-1*WEEKDAY('Date'[Date],2)+1
Week End date = 'Date'[Date]+ 7-1*WEEKDAY('Date'[Date],2)
Week Rank = RANKX(all('Date'),'Date'[Week Start date],,ASC,Dense)
OR
Week Rank = RANKX(all('Date'),'Date'[Year Week],,ASC,Dense) //YYYYWW format