Installing MLB (Mouseless browsing extension of Firefox)
This extension can be installed most easily by following the steps below.
Choose Tools -> Add-ons in Firefox.
Click on "Get extensions" (top left)
Search for mouseless browsing
Locate the MLB search result, possibly search ones more for the same text.
At the bottom of the page choose Install Now
In the Firefox dialog box (after a short time) again choose Install Now
Finally restart Firefox
Now you can by hand toggle the numbers by pressing the "." (Del) key of the numeric keypad, with Num lock on.
The speech commands should now also work. If not try to restart NatSpeak.