Marker : Fix typing

[Fridus]

Hi,
It solves this error:

error TS2345: Argument of type 'Marker' is not assignable to parameter of type '{ top: number; left: number; }'.
   Types of property 'top' are incompatible.
     Type 'Number' is not assignable to type 'number'.
       'number' is a primitive, but 'Number' is a wrapper object. Prefer using 'number' when possible.