The ranges are due to the enormous stretchiness of the sheets. Hence, they will adjust to
the exact contours of your mattress and will accommodate your bed's size perfectly.
Exact Mattress Size Ranges for King, Eastern King, California King, Western King Sheets are:
Width:   For Mattresses between 71" and 79" (inches) wide (180 to 200 centimeters)        
Length: For Mattresses between 78" and 87" (inches) long (200 to 220 centimeters)        
Depth:   For Mattresses between   6" and 18" (inches) deep (minimum and maximum
recommended mattress thickness) (15 to 45 centimeters)
.com
®