Some players don't build the starport directly after the colonization - leaving the planet empty until certain popgrowth has been achieved. This way, an excessive Colony Rush can be done without taking the economy down too much.
Planets without a starport will show the MP in brackets. It is not used, and you don't pay for it. This applies also when there's no ship in the starport queued.
The number which is shown in the brackets is the base MP - although put to the power of your civ-wide sliders.
