I sent an email enquiring bout the test and here was he reply:

Your email is strange because the definition of aptitude in the Dictionary. It is either the you do not understand English or there is some ego problem in display.

However, for academic sake, aptitude simply means written calculation test. It could be objective or theory.

#if this is how they respond to applicants, I wonder how they treat their staff.

They asked me to come with a calculator. Apparently the invite is for an aptitude test.