Perfectly understandable. "10 foot cube" and "10 cubic feet" are very similar phrases.
As for what effect it would have on the surrounding material - exact effect (if player doesn't specify) is DM descretion, but the spell doesn't create stone - it shapes it. Whatever segment he touched now has an approprietly sized hole, as that was the material pulled to make the wall.
Edit: and for how long it takes to breach a Hardness 8, HP 30 section of wall (on average):
Figure the damage range for the attacking critter (e.g., we have a medium Str 14 cleric with a +1 Mace - +2 Str, +1 Enhancement, base 1d8; damage roll is 1d8+3) and figure what portion of that would penetrate the hardness (1d8+3 penetrates hardness 8 on a roll of 6, 7, or 8, for 1, 2, or 3 points of damage, respectively) and what that will average per hit (there are 8 possible rolls, 3 of which do damage; we have (3+2+1+0+0+0+0+0)/8 damage per hit, or 6/8 pts/hit) and figure how often hits will happen (we have a Large (?) wall (-1 AC), it's an inanimate object (dex 0 -5 AC; additional -2 penalty as well) and has a base of 10 - which means it has 10-1-5-2= AC 2. Virtually any character will only miss on an automatic miss - a roll of 1 - as objects aren't subject to criticals, this means that the cleric will be getting 95% hits, or 100%, if taken one hit/round as a full round action) and multiply the two together to get your damage per attack ((6/8)*(19/20)=0.7125 damage per attack). Multiply that by the number of attacks per round that fit the criteria (for each given attack bonus/damage combo - as this wall can really only be missed on a roll of 1, we can just full attack - although if we only get one attack/round, might as well full-round it to get a gaurunteed hit; let's say the cleric gets two attacks/round - this means the cleric, by himself, is dealing 0.7125*2=1.425 points of damage/round (on average)). To get the expected time it takes to breach the wall, add up the damage/round for each character attacking the same section, and divide the resulting number by the HP of the wall (if we only have the one cleric, then that 30 HP will take about 21 rounds to breach the wall (30/1.425)). Chances are, that wall is still up after four rounds.