It depends very much on the brand/source of the mineral water. There’s usually a list of minerals, with details of the concentration of each, listed on the label.
Also, the kidneys are very efficient at pulling excess minerals out of the blood or holding onto them, based on the blood concentration. Sodium, calcium, potassium, magnesium, etc. have to be maintained within narrow limits in order to support life. Of course, damaged kidneys are less able to regulate mineral concentration within these limits, so people with known kidney disease may want to avoid mineral waters.