OLC's GUI AoB Calculation - Please Help!

[siber]

Hi guys...

A quick question about OLC's GUI calculation of AoB, for those who use it. I was hoping someone could go through my method and check my working because I can't understand where I'm going wrong!

Below you can see me lining up for a shot at a Large Merchant. You can see that the AoB is somewhere close to 90 degrees. The range is estimated via use of the vertical ticks (about 1.5 ticks)


Now, I move the centre ring so that 1.5 is opposite 90deg on the bottom ring:


...and can estimate the range from the mast height (33.2m) on the outer ring. The range is just over 5000m


Now I drag the 5000m+ mark round to meet the ship's length on the outer ring (155m)...


As the ship is 10 points from the centre, the AoB should be indicated on the lower wheel by the 10 on the bottom centre wheel. But it's not! Why???


Please could someone explain why this isn't working for me, as it's driving me nuts! I'm relagated to setting up a position so that ships pass in front of me at as close to 90 deg actual AoB as possible and this is very limiting when I need to take a shot at funny angles or zig-zagging targets!