Don't miss the fact that the glideslope is setup at an angle of 3.33 degrees instead of our standard 3.00 degrees! So, BOAC, I realize you have some deficiencies in mathematics: 330 ft/NM * 8.7NM = roughly 2900ft difference in altitude. Add the THR elevation and you get to about 4600ft. Easy, isn't it? Maybe you should go back to the books to review basic IFR procedures and how to check the profile of an approach...