Basically, closeness is represented by Matching Percentage. However, you should also take Confidence into account, which shows how reliable the result is. Following are the brief description of each parameter.
Matching Percentage indicates the closeness between the input image and reference images in the database. Its takes values in the from 0% (least close) to 100% (closest).
Confidence indicates the degree of reliability of the result. Confidence is calculated based on the proportion of images close to the input image in the database. It takes values from 0% (least reliable) to 100% (most reliable)