Tan line on 13 month old?

I feel so bad, and so confused! I took my son outside in his pool today. He had his trunks on, and a swim shirt. We were out there maybe 45minutes to an hour. If that. I put sunscreen on him probably 3 times during that hour. Lol. And I come take his swim shirt off when we come in, and he has a tan line??? Not a burn at all, but I feel so bad! Is this normal with sunscreen?? I put it on him so much! Maybe because he is Hispanic and will tan way easier? I dont know. I just feel bad 😭😭