Wrong distance shown in miles for extension earthdistance

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Page: https://www.postgresql.org/docs/10/earthdistance.html
Description:

Hi,
 I have installed 
CREATE EXTENSION CUBE;
CREATE EXTENSION earthdistance;

Post which I ran the following query:
SELECT (POINT (19.974, 72.756)<@> POINT (19.195, 72.959)) AS DISTANCE;

The answer came back as 21.17534 miles whereas the actual distance (as crow
flies) is 55.42 miles which I have checked from 2-3 websites. (Google maps
gives a greater distance which is travel by road & this value has been
ignored).

I know both the places and the distance between both of them cannot be 22
miles. It has to be in excess of 50 miles atleast. What am I missing?