There are two main tests used to determine indentation.
The first tests static load, which tests at very high PSI whether the product punctures. This doesn't mean the weight won't leave a mark, but it does mean the product can hold the permanent weight and still be functional. Modin at 720 PSI has a result of 0.24 mm, meaning 720 lb concentrated on one square inch will dent the surface down 0.24 mm, or 0.009" (after a 24 hour recovery time).
The second test that is used is residual indentation. The vinyl wear layer has a unique property that means that dents may show up, but bounce back after allowing time to rest. This phenomenon can be amplified and sped up if the floors are exposed to heat, which will soften the wear layer and cause it to regain some of its memory.
This "rebound" effect is very real, but can be limited and vary depending on the construction of the product. The standard test is ASTM F1914-17. The test is meant to mimic the weight of a high-heel, or a rock stuck under a shoe. A 4.52 (1/6") diameter indenter is weighed with 140 lb and left on the floor for 10 minutes. It is then removed, and the floor is allowed 60 minutes to recover. The remaining indentation is measured. With Modin, there is a remaining indentation result of 0.1 mm (1.4%)