This does not limit the wifi speed directly. All you can do with this router is attempt limit your upload speeds. If your attempting to limit download speeds or wifi traffic within your house it can't be done on this router.
To a point you can limit the upload traffic speeds...I think. MBS means maximum burst size. If you were to set that to the value you did not want some traffic to exceed it should work. You would still have to identify traffic and match it to this rule. You normally can only restrict based on mac address or ip address.
I strongly suspect like most people that ask this question you want to do limit something other than your upload speed so these settings are pretty much worthless.