Wild guessing here, the bottom row probably is the 6 (7 segments, 6 of those are "on"). The first digit needs to be on the top row somewhere. I'm not sure whether the display has an option to show 2 different numbers based on the turbo status.

I would experiment by removing all the jumpers, then replacing one at a time to see which element is on in which state.

This isn't the same, but might be similar: http://minuszerodegrees.net/led_speed_display … 0-%20SD-402.jpg

When it shows 16, is the '1' the two left hand, or the two right hand vertical bars? Assuming the normal 'T' shaped layout of the pins along the top and bottom (although starting at the top-right bar, rather than the top bar), it looks like it's possibly set to go between

1     _           _
2|   |_  and     |_|
3|   |_|         |_|

I guess the problem is more that it's not switching between the two values, which you'll need to know what the pins on the side do. Do you have a multimeter? First step might be to check if any of the pins connect to the ones that might be +5 and GND.