Accuracy by Position

I'm wondering if I have an exceptionally good movement or a really bad movement. I have a Phylida Seamaster GMT homage that loses 15-20 seconds/day when I place it crown down and gains 15-20 seconds/day face down. I have a haq Certina that I look at when I put the Phylida down and if it's running fast I place it crown down, if slow face down and it stays perfectly accurate. Right now it is correct to the second. Is this common? I have been doing this for several months and it has always been within 15 seconds using this method.  

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Watches run at different speeds depending on the position. This is quite common. When adjusted they are so in different positions trying to balance the "slower" positions with the "faster" ones to reach the desired average. However people to usually always use the same amount of position time, so this may vary. If over a time you know that wearing the watch and letting it resting during the night face up, or crown up, and on average it runs, say 15 slow, to the average while adjusting, to the result in the different positions to a +2 sec a day, you may add 15 seconds to the face down position (while adjusting the lever). So at the end, with time and patience you can pretty much forget about the differences or get used to put the watch as you do.