Silicone tips on Airpod Pros 2nd gen

I bought my Airpod Pro 2nd Gen off of Amazon- Amazon Renewed. They came with the medium size tips on. They seem to fit my ears at first, but after awhile they become loose and fall out. So naturally- I wanted to try putting on the next size up tips, the large. But the large silicone tips do not line up at all. The medium ones easily click and line up on the Air pods. The large silicone ones click, but they are not lined up and I cannot get them on straight.

Two questions. One- how do you know what size fits your ears? Yes, the medium size works for the noise cancellation seal so the fit test says they fit- but after awhile they get loose. I have to squish them into my ears to get them to stay, which doesn't seem normal.

Second question - why are the medium tips lining up perfectly but the large ones do not fit? They click on, but they do not line up properly and they're crooked. Do you think the product gave me the wrong tips?