The different number of ATP molecules formed through cellular respiration is due to the varying efficiency of each stage in the process.

Cellular respiration is a multi-step process that converts glucose into ATP (adenosine triphosphate), which is the main energy currency of cells. The process consists of four main stages: glycolysis, pyruvate decarboxylation, the citric acid cycle (also known as the Krebs cycle), and oxidative phosphorylation.

1. Glycolysis: This is the first stage of cellular respiration and it occurs in the cytoplasm. One molecule of glucose is broken down into two molecules of pyruvate, producing a net gain of 2 ATP molecules.

2. Pyruvate Decarboxylation: In this stage, each pyruvate molecule is converted into an acetyl CoA molecule, which is then used in the citric acid cycle. This stage does not directly produce ATP.

3. Citric Acid Cycle (Krebs Cycle): This cycle occurs in the mitochondria and produces 2 ATP molecules per glucose molecule. However, it also produces NADH and FADH2, which are used in the next stage to produce more ATP.

4. Oxidative Phosphorylation: This is the final stage of cellular respiration and it produces the majority of the ATP. It occurs in the mitochondria and uses the NADH and FADH2 produced in the previous stages to produce ATP. The exact number of ATP molecules produced in this stage can vary, but it is typically around 28-32 ATP molecules per glucose molecule.

So, the total number of ATP molecules produced through cellular respiration can vary, but it is typically around 30-36 ATP molecules per glucose molecule. The variation is due to the efficiency of each stage in the process, as well as factors such as the availability of oxygen and the type of cell in which respiration is occurring.