Unfair Loss in Savings of Life

On his 20th birthday, Ajay started depositing Rs.500 in his saving box. His brother Vijay used to withdraw Rs.100 from the same box on his birthday every year. On his 60th  birthday, Ajay opens his box & finds only Rs.1000 in it.

How this could be possible?

Two brothers at old age
Ajay & Vijay
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