The upper cervical process is slow. There are ligaments that need to tighten/heal to hold the atlas in position. The leg length check system is very good at identifying problems.

Your atlas subluxation may or may not contribute to your dizziness and fog. You just have to try to see. I suggest you ice your neck after each procedure. The goal is two fold. Get the atlas in proper position and reduce any inflammation due to atlas being out of position.

If inflammation in your upper neck is a contributor to your dizziness and fog, it can take a while for the inflammation to subside.

You sleeping and resting posture can impact how long it takes for atlas to stabilize in proper position.

It sounds like the chiro only worked on your atlas but nothing else in your spine. These kinds of chiros believe every problem comes from atlas. Fix atlas and the rest of the spine will self-correct. That is an extreme view of the spine. Many upper cervical chiros combine atlas work with working on the rest of the spine. Personally, I don't put a lot of confidence in the atlas only concept. It is fine for those issues related to atlas but not for issues related to the rest of the spine.