Anyway, I am fine with the smaller area, which makes fine sense to me, but I came across another spell that has an area of "30-ft. cube/level" and was wondering if a 30-ft cube meant a cube that is 30 ft. on each side (i.e. 30 ft x 30 ft x 30 ft)? At the very least, I assume it is different than 30 cu. ft. since it is written differently, but I want to make sure my interpretation makes sense.
I am convinced that a 30-ft cube means 30x30x30, just as a 10-ft square means 10x10 sq-ft.
Whether or not there is spells where 30 cu. ft is a mistake, is hard for me to say, but per default I'd expect the game designers to have the measurements right unless it is contradictory.As such, I fully agree with your interpretation.
Since it is worded differently, we have to assume the designers knew what they were writing and did in fact intend for it to function differently.
It's the smaller area. A cubic foot is a 1 ft x 1 ft x 1 ft cube, so the spell covers an area of 10 of those, plus an additional 1 cubic ft/level.
It's great for creating a door-size opening in a wall, one of the most common uses, but not so good for creating a tunnel, since to make it usable by a medium sized creature, a 14th level caster would make a tunnel only 2' long/deep (Assuming it was 6' high and 2'wide, about the size of a big fighter in armor). If the character were willing to crawl, you could get by with,say, a 2' x 3' opening (6 cubic feet) and make a 4' deep tunnel.