It corresponds to the number of lane (= fraction) on which you want to load your pool of libraries.

It corresponds to the name (= identifier of 8 characters maximum) given to the submitted pool.

Example
If you want to sequence 24 libraries with around 30 M reads each, please fill as following.
• Nb of lanes = 2
• Multiplex # = 24
• Multiplexing group = ex: date & initial = 010223XX