The degrees for write are always relative to the values you pass in the attach function. If you don't pass any values, the defaults of the library will be taken. So in this case, always pass them.
The values you use for attach are pure garbage if you're using a standard RC-servo. They should be the number of microseconds for the low and high positions (usually 1000 and 2000).
As an alternative, use microsecond values for write or slow-move. Those bypass the conversion magic an permit a better control. Usual values are from 1000 to 2000.
Korman