I have a 94 Subaru Legacy automatic I just put a new battery in. Being in a hurry I went to the website of the national parts chain store nearest me, put in my vehicle info to get a list of what they claimed is compatible, picked a middle-priced one that was in stock, got it and installed it. It seems to work fine. But, then I double checked the car manual and it says this version (4 speed auto) wants a 118 reserve capacity, and the battery I got says it's 95. Furthermore, none of the batteries they sell that say they're compatible are 118 or greater; the highest is 110, and most are 90-100. Does it just not matter? Was there some kind of trend towards smaller-than-spec batteries?
So, it should work fine, but the extra capacity is probably specified for several reasons.
Such as cold winters - a higher capacity is required, if it does not get too cold where you are then it should be ok.
Also, it's automatic so bump-starting is not possible and extra capacity is normally specified - same for diesels as they need more oomph.
Some of the parts store info charts / books tend to go for the lowest, smallest, cheapest option but, as said above, it should be fine - just don't leave the lights on !!