The four minimas you have shown on the chart (The A, B, C, D things) are for four ICAO aircraft performance categories, determined by the approach speed of the aircraft.. .. .Category:. .A - Vat up to 90 knots. .B - Vat from 91 to 120. .C - Vat from 121 to 140. .D - Vat from 141 to 165. .E - Vat from 166 to 210. .H - helicopters.. .. .(Where Vat is the speed at the threshold based on 1.3 times the stall speed in the landing config. at max weight.). .. .So if you are flying a cat B aircraft, you fly the aproach to 635 feet AMSL (in your example), in a cat C aircraft you would fly the approach to 647 feet.. .. .In your example, the airfield elevation (at the aerodrome reference point) is 488 feet, and this is the difference between the altitudes and heights you have listed. (i.e. 625-147=488, 635-157=488 etc.)