I wouldn't worry to much about that difference as different wireless manufacturers use different methods to do do the calculation and as yet they are not very accurate.
Where the antenna is located in the laptop may also have an effect, try slowly turning the laptop round and watch to see if the signal varies.
You could also try another couple of tools and see if they give different results:-
1.Inssider
Inssider | MetaGeek
2.Xirrus wifi-monitor
Advanced IT Wi-Fi Networking Tools - Xirrus Wireless LAN

As a point of interest the free space loss at a frequency of 2.4GHz and a distance of 0.001 miles, 1.76 yds, is 44.2dB's. This means that if your laptop is 1.76yds from the router the signal from the router has already been attenuated by 44.2dB's before it reaches the laptop.