I’m quiet confused here because I paid Zakat just once in my life and it was last year

I?m quiet confused here because I paid Zakat just once in my life and it was last year, it was not because I was lazy but because I have never reached the Nissab before ? anyway to explain well my confusion I need to give you an example and you could answer me appropriately and quickly because I need to pay my Zakat now Let?s say the Nissab of the Zakat is $50 ?. And say also I usually pay my Zakat on Month12 (it?s not really December but it?s just an example). I got $50 in Month12 / 2001 In Month12 / 2002 (it?s one year now that I possess $50) I paid 2.5% of it ? Month01 / 2003 savings $10 Month02 / 2003 savings $10 Month03 / 2003 savings $10 Month04 / 2003 savings $10 Month05 / 2003 savings $10 Month06 / 2003 savings $10 Month07 / 2003 savings $10 Month08 / 2003 savings $10 Month09 / 2003 savings $10 Month10 / 2003 savings $10 Month11 / 2003 savings $10 Month12 / 2003 How much Zakat should I have to pay?? And could you please illustrate an example for me so I understand well how it works