How to change Tempo on Garageband tracks without speeding up my Input Track

I think this is a pretty simple question. I am sampling some sounds off of old vinyls I have through the Line Input Track option. I've been trying to use the tempo adjuster to change the BPM to match the BPM of the samples, but Garageband speeds up the samples instead of lengthening the region. Is there an easy way to fix this?