remember when you doing your calculations you then need to make sure you have enough ram. Lets say PCQ-TOTAL-LIMIT=x
RAM required = x*(2000Byte+200Byte) (2000Byte buffer for 1 packet. 200 Byte service data for 1 packet)
Ram required = 51100KiB*2.2 = 112420 Kib = <112.4 MB Ram required if you have 1022 people concurrently online at one time. It is covered under this page. http://forum.mikrotik.com/t/pcq-limit-total-limit-settings/12002/1 If you look at https://mum.mikrotik.com//presentations/US08/janism.pdf There is more detail.
how is your customers performance now.