Please see 2015 ASME Section IX. Notch toughness is impact testing
QW-200.3 To reduce the number of welding procedure
qualifications required, P‐Numbers are assigned to
base metals dependent on characteristics such as composition,
weldability, and mechanical properties, where this
can logically be done; and for steel and steel alloys (Table
QW/QB-422) Group Numbers are assigned additionally to
P‐Numbers. These Group Numbers classify the metals
within P‐Numbers for the purpose of procedure qualification
where notch‐toughness requirements are specified.
So to weld P-No 1 Group 1 to weld to P-No 1 Group 3 for impact qualification, you need a P-No 1 Group 1 to P-No 1 Group 3 WPS.