Sonal as an FYI, you cannot confirm birth-time from an existing kundli accurately always (you/family members gave input to it; so if input given was wrong, we will get wrong output). You need to validate with family and check timing of certain events to confirm horoscope is at cusp of change of rising sign.
Astrologers on this group have seen several instances where timing insisted by qeuerent was wrong despite repeated confirmations with family members (example: difference btw when child is born and when he is introduced to family by doctors or family/doctor not remembering it correctly).
Birth time rectification is a tedious exercise & is advised by a good astrologer close to your place.
God Bless,
Astrologer Deepak