I looked further into Dendrochronology, or tree-ring dating.

Via Minnesota Department of Natural Resources

Sometimes you may notice a ring with wider growth on one side and narrower growth on the other (A). Competition from other nearby trees can cause this condition. Sometimes uneven growth rings result when one tree falls and leans against another live tree and the live tree grew more on one side to curve up around the fallen tree. Other explanations may include a tree growing on a slope or on slumping ground, or a windstorm may have pushed the tree to lean to one side. When that happens, the tree lays on thicker growth on the side closest to the ground in an effort to grow upright again.

So knowing the sample I brought in last night was from a branch, the thicker rings are then on the underside of branch, as they grow quicker to keep up with the top of the branch, to keep the leaves close to the sky, the sun & the rain.