With each 3db representing a doubling of signal, these figures would equate to a wireless signal of 64 times as strong, which takes some believing.
Well i can only tell you what inSSIDer is reporting, believing it or not is your choice, but don't forget these results are using the RSSI off various consumer network cards, not a million quids worth of Arqiva test equipment.
Its just shown -25dBm up against the HH4 and -58dBm in the bedroom furthest away from the HH4. Whether the numbers reported are accurate or not is irrelevant given the numbers reported in the bedroom using the HH3 were worse by a significant amount. The point is the HH3 was worse.
Even if i just rely on WiFi signal indicators on different devices the signal strength is clealy higher using the HH4 over the HH3 so unless the HH3 had some voodoo ESP paul daniels powers going on where it could suppress the signal strength indicators on various devices then i can only assume the HH4 distributes the WiFi signal in a more efficient manner.