Your math is ok as far as it goes but it does not take into account the differences in how the AH and RC tests are performed. RC is measured at a constant 25A discharge rate, which is a fairly heavy load and similar to what you might expect with an inverter running a tv and satellite receiver plus a few background Dc loads (lights and such) or about 300 watts. AH, on the other hand, is measured at a much lower discharge rate, typically around 5A. It is defined as the the number of AH provided over a 20 hour time period, so an AH of 100 means it delivered 5A for 20 hours. 120 AH means 6A xr 20 hours, and so on.
The difference in the measurement technique is important because a battery can deliver many more AH at a low discharge rate than a high one, often substantially more. So a battery with an RV of 182 is probably closer to 90-100 AH than 75. For example, a Trojan 27TM deep cycle has an RC of 160 and a AH rating of 105, while a Trojan 27AGM has an RC of 175 but an AH of 100.
Also, I disagree that an RC rating indicates a starting battery. RC was invented in an attempt to standardize battery capacity ratings so that apples to apples comparisons could be made. Since each battery is discharged at a different amp rate in the AH measurement, it is not really an exact comparison. Some manufacturers adopted the RC measurement and others stayed with AH. Some of the very best battery brands give both, e.g.Trojan and Lifeline.
None of this answers the question "is it a good battery?" You can compare it to other NAPA batteries and learn something about their relative capacities, but if you want a really top quality deep cycle, I would shop at a different store. Trojan and Lifeline are some of the very best. Interstates 6v golf cart batteries (U220, U2600) are also very good, but that does not mean their entire line of batteries are good. Trojan's MinnKota trolling motor batteries are also quite good deep cycles and sometimes found in Walmarts or KMarts at attractive prices.