Say you put the input percentage in K1

then in say, I2 enter:

=IF(A3=A2,"",IF(COUNTIFS(A$1:A2,A2,H$1:H2,">"&$K$1),COUNT(I$1:I1)+1,""))

This identifies the last date record of the group where one of those dates surpassed the percentage you input into K1.

copied down

Then to get the count, in a separate column:

=MAX(I:I)