You can try these expressions in your placeholders.
W: =FLOOR(Fields!Downtime.Value/10080)
D: =FLOOR((Fields!Downtime.Value - (FLOOR(Fields!Downtime.Value/10080))*10080)/1440)
H:=FLOOR((Fields!Downtime.Value - ((FLOOR((Fields!Downtime.Value/10080))*10080)+ (FLOOR((Fields!Downtime.Value - (FLOOR(Fields!Downtime.Value/10080))*10080)/1440))*1440))/60)
M:=Fields!Downtime.Value - (((FLOOR(Fields!Downtime.Value/10080)*10080)+ (FLOOR((Fields!Downtime.Value - (FLOOR(Fields!Downtime.Value/10080))*10080)/1440))*1440)+ (FLOOR((Fields!Downtime.Value - ((FLOOR((Fields!Downtime.Value/10080))*10080)+(FLOOR((Fields!Downtime.Value - (FLOOR(Fields!Downtime.Value/10080))*10080)/1440))*1440))/60)*60))
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