Dish azimuth

[patmos]

I am in Mauritius (indian Ocean) and want to point my 12 ft c band to true North. I have some problems with Mauritius: Satellite map, lat and long, and satellite TV dish pointing in Mauritius
It gives the following:
Latitude = -20.1436, Longitude = 57.5491
Lat = 20 degrees, 8.6 minutes South
Long = 57 degrees, 32.9 minutes East
If you want to point a satellite TV dish at the Satellite at = 57 East orbit longitude

Dish elevation= 66.4, Azimuth= 20.8 (magnetic compass), Polarisation= -1.5

Polar mounts only: Main angle= 20.6, Downward tilt= 3.0, Motor drive sideways angle= -0.6

From Satellite Alignment Soft(SAA)
I get this without the magnetic declination

57,0°E - NSS 703 Az 358.621 ° EL 66.288
adding 18 deg for magnetic declination would give me 358.621+18 = 16.621 ( magnetic compass) anyone to explain why satsig gives (20.8 instead of 16.21 or 16.8)
For elevation it's ok 90 - 20.6 - 3= 66.4 (or 90- 23.6 = 66.4)
Got this diagram from the internet help me understand the concept of polar axis angle and look angle.

 

[patmos]

I finally got the answer from Eric Johnson telling me that there are some errors in magnetic deviation for some parts of the world in his program. So that accounts for this. Thanks to all