What do I do if the round had multiple closings?

There are two options here, and the choice is yours. You can create a single round and use the date closest to when you made your investment, or you can create multiple rounds.  If you invested in only one closing, a single round is simpler and recommended.  If you invested in both closings, it may be clearer to list them separately unless everything about the rounds was identical, in which case you could combine them into one round using the later date and add a note to yourself to remind yourself that you actually had some of your funds in the earlier closing.