Official rule text
68.1 A unit’s “Production” ability, which is presented on a faction sheet or unit upgrade technology card, is always followed by a value. This value is the maximum number of units that this unit can produce. a If the active player has multiple units in the active system that have the “Production” ability, that player can produce a number of units up to the combined total of their units’ production values in that system. b When producing fighters or infantry, each individual unit counts toward the producing unit’s production limit. c A player can choose to produce one fighter or infantry instead of two, but must still pay the entire cost.
View official source
Source: Living Rules Reference and FAQ - Prophecy of Kings
Expansion: Prophecy of Kings
Version: 2.0
Reference: Rule 68.1