How to raise alkalinity without raising PH?

I tested my water tonight and everything was spot on other than the alkalinity being pretty low. I find it odd since the PH is at 8.0, but the ALK is 4.1.

I would add buffer, but I'm afraid I'll throw off the rest of my parameters? I'm thinking I'll test the PH again in the morning and see what results I get, but if they're the same I'm hoping for a solution. Thank you!