80211n begginer question

What is this HT MCS and HT-amsdu-limit(threshold) option? What stands it for? What is the explanation?
Big thanks!

http://wiki.mikrotik.com/wiki/802.11n_Setup_Guide

It’s too shot:

Non-Winbox viewable configuration options
ht-amsdu-limit (0..8192)
ht-amsdu-threshold (0..8192)
These last two only appear in terminal at this time. (ROS4.0beta4 made these configurable in winbox too.)