The magnetic field of Earth can be modelled by that of a point dipole placed at the center of the Earth. The dipole axis makes an angle of 11.3° with the axis of Earth. At Mumbai, declination is nearly zero.

Then,

The magnetic field of the earth represented as below:

The earth is taken as a dipole (in theory) at the center. The angle of rotation of the earth does not coexist with the earth’s magnetic field. Therefore, the axis tilted at 11.3° from the axis of the earth. Now as the angle of declination in Mumbai is nearly zero, hence, the difference between the angles is equal to 11.3° from the axis of the earth either in west or in east.