There's one number that's common between both batteries - the amount of Amp-Hours the battery can deliver over a 20 hour constant discharge. That's Capacity -20 for the Interstate, Capacity at C/20 for the Deka.

The Interstate L-16HCL is rated at 420 amp-hours, the Deka is rated at 370 Amp-Hours. In other words, the Deka battery stores 13% less power than the Interstate.

The rest of the numbers are just different ways of measuring the battery capacity.

Interstate rates their batteries using Reserve Capacity, which is an easier test to administer than the 20 hour constant discharge test. Reserve Capacity places a 25 amp (or 75 amp) constant discharge on the battery, and measures how many minutes it takes the battery voltage to fall to 10.5 volts. That's the Reserve-Cap 25: and Reserve-Cap 75: numbers.

The 20 hour Amp-Hour test is more complicated to perform, you have to estimate how many Amp-Hours the battery can deliver, then test it for that length of time. If you guessed wrong, you have to do the test again at a different Amperage, until it takes exactly 20 hours to go from full charge to discharged.

Complicating the issue is batteries deliver more power when they're slowly discharged than they do when they are discharged more rapidly. It's called the Peukert effect after the guy who discovered it, and is why you can't directly convert Reserve Capacity into Amp-Hours unless they both happen to use the same discharge current.