Well, it certainly meets the specs on the page, but it is only 13300 mAh at 3.6V, not 9V. At 9V, it is 5400 mAh. Price seems a little high for that capacity.
I'm not sure this is exactly right either. Based on what I know about the 18650 battery cells, which is what these DVD batteries are made from, the highest mAh rating out there is 5000 mAh @ 3.6 volts. I am not exactly sure where the battery manufacturer is getting their ratings and that is where the confusion comes in. The DVD battery is 3.6 x 2 = 7.2volts and then they step up the voltage to 9 volts. When you step up the voltage you "step down" the mAh capacity. SO, the highest capacity cells would give you 15,000 mAh rating which would be about right for a 9 volt DVD battery rated at 13,300. We don't know the exact formula to adjust for the voltage conversion done internally in the battery. The real kicker is that 48Wh rating does not match anything. And if that number is correct then the battery really works out to about a 4200mAh battery. Which is on the low side of DVD batteries. OR depending on how they arrived at that number it works out to about 10,000 mAh @ 9 volts. Most that we use are 5400 and 6000 mAh rated. Those batteries use the 2000 and 2400 mAh cells. This is just more confusion since there is no "standard" way to list battery capacities so a manufacturer can work the gray area's to make a battery look like it is bigger than it's real world application reveals. The only way to be sure would be to see if the batteries in the that new DVD battery actually had a rating one them. BUT even IF you open it there is no guarantee that the battery will have it printed on it.
I think Kirk is on the right trail, though I'm not following everything.
Overall, I'd say the 48Wh is an accurate description, and this is basically the same DVD-type battery in widespread use at ts.com -- namely, 9v and 5400mAh.
48Wh could be a slightly rounded figure, say it is actually 48.4Wh, or 48400mAh: at 9v, that is a capacity of 48400/9 = 5378mAh, or again rounding, 5400mAh -- same as the typical DVD battery.
As for the 13,300mAh spec'd rating: 48,000mWh/13,300mAh = 3.6V, which is the voltage of a typical, single Li-ion cell. Pretty sketchy marketing, but the battery probably has 13,300mAh of capacity internally, except that that is at 3.6v, not 9v, and needs to be stepped up.
As Kirk notes, step up the voltage, and you need to step down the mAh capacity at that voltage. Worse, a DC-DC step up circuit will not be 100% efficient, so if you step a 3.6v battery to 9v, you'd need to multiply the 3.6v mAh capacity by 3.6/9 to get the new 9v mAh capacity, and then multiply that again by say 90% (total ballpark here) to account for the inefficiency of the DC-DC converter. If there really are 13,300 mAh of 3.6v cells inside, that would be 13,300*3.6/9*0.90 = ~4800mAh, or only about 43Wh total capacity.
Hopefully, they are putting in something like six 3.6 V, 2500mAh capacity Li-ion cells, which would yield 6*2500 = 15000 mAh capacity at 3.6v, or at 9V: 15000*3.6/9*0.90 = 5400 mAh capacity at 9v, or ~48Wh capacity as labeled.
Bottom line, this is most likely just a 9v, 5400mAh very typical DVD battery, with some pretty sketchy marketing.