A Gamut Check allows you to check if colors are inside or outside the gamut of a given profile (which can be a 3, 4, 5, 6 or 7-color profile).
The example above shows how PANTONE colors will be simulated.
For every PANTONE, the Gamut Check window tells you:
You can also check the percentage of inks under a certain delta E.
Double-click an ink to compare the Lab and LCH values of the original and the converted ink, and to see the difference visually.
Based on this you may decide to change a color strategy's rendering intent, or to use custom values for this ink.