Try

=COUNTIFS('Data entry'!P:P,">=" &TODAY()-7,'Data entry'!P:P,"<=" &TODAY())

This is last 8 days so change ">=" or "<=" as required

For previous month

=COUNTIFS('Data entry'!P:P,">=" & A1,'Data entry'!P:P,"<=" &EOMONTH(A1,0))

where A1=Start of month date e.g. 01/02/2017 (1st Feb)