When someone says, "it was really nice seeing you," it generally means that they enjoyed the time they spent with you and appreciated the opportunity to meet or catch up. It's a polite and friendly expression commonly used when parting ways after spending time together.
This statement suggests that the person had a positive experience during the encounter, and they may have found your presence enjoyable, engaging, or meaningful. It can be used after various types of interactions, such as meeting up with a friend, attending a social event, or even after a chance encounter with someone you haven't seen in a while.
Overall, it's a pleasant way to acknowledge the time spent together and to express a positive sentiment about the encounter.