This motion increases the active collator set size to 12, i.e. every round (currently approximately 2 hours) the top 12 collators by total stake (self stake + delegated stake) will be selected as block authors during the next round.
Zeitgeist would like to increase the collator set size during the course of time to achieve more robustness and decentralization in the network. The increments should happen in small steps to ensure, that the network is capable of handling addition collators without experiencing drawbacks.