7-speed FWs fit in 126 mm spaced dropouts. 126 mm was adopted in the early '70s to accommodate 6-speed FWs using the same spacing as 5-speed FWs. Late '70s SunTour, then others started making narrow FWs such that 6 cogs now fit in bikes spaced for 5 and 7 cogs in the space for 6. So using the old terminology, that Univega is a 6-speed spaced frame with a 7-speed FW.

The bike looks like it was from the early '80s when 7-speeds were pretty new and 126 spacing was universally called "6-speed".

Ben