How to CIR and How to shared bandwidth in mikrotik?

Thank you very much for reply of my previous question. sir now i m using winbox to assign bandwidth to the clients in simple queue, there are two TABs one is general and 2nd is advance. they both TABs have bandwith option as max-limit and limit-at,
when i sign bandwidth max-limit 256/128 then limt-it bandwidth become unlimited, i m confuse amongs these because i have clients that need CIR and some clients need share. so what should to do for that.

please help me…

Limit-at is CIR.
Max-Limit is MIR.

Set Limit-at to provide CIR, then configure Max-Limit, which will be provided based on priority.