IRS Review letter was sent to me, after I have already received my refund?

I had filed for my taxes on 1/30 And a few weeks later I had called, and they had told me I was selected for review and to wait up to 45 days. Long story short, I finally received my tax refund on 3/14. Then I received a review letter in the mail dated 3/9 saying I was selected for review. The letter states after the review my refund may be sent to me, and I don't need to take any action at this time. Was it possible the letter inter to be sent to me before my refund? I don't know why they would send me my refund if everything didn't check out. I'm worried about this, do I disregard? Thanks for the help everyone!