Peter asked if he was to forgive his brother (Israel)
for 49 (7 x 7) consecutive years - until occurrence of the Jubilee Year (Leviticus 25:11-13)
Jewish debtors, with the knowledge of the Law (Romans 2:23),
were forgiven after 49 (7 x 7) years (Leviticus 25:8-10), whereas their ignorant Gentile oppressor (Nebuchadnezzar) was forgiven
after 7 "times", i.e "years" (Daniel 4:16,23,25,32)
Christ responded that Peter was to forgive his brother
(Israel) for 490 (70 x 7) prophetic years - until establishment of Messiah's everlasting kingdom
of righteousness (Daniel 9:24)