what is calls-in-arrears?

If any body purchase the share of a company whose per share
value is Rs.10 (Rs 2 on application,3 on first allotment &
Rs 5 on final call)and company demand the the value of
application & first allotment i.e. Rs. 5 but person who
purchase one share pays Rs 2 only in stead of Rs.5.So Rs.3
will be calls in Arrear.