This reference image shows a bridge of maximum length, with 5 blocks to either side of the sign, making for a bridge 11 blocks wide. Valid numbers are from 0 to 5 for each line. The block the sign is on is always included, so a [Bridge] sign with 0 0 as its 3rd and 4th line values will be 1 block wide, the block the signs are on.
A [Bridge] sign with no values in the 3rd and 4th line assumes 1 block to the left and right of the sign; and, in fact, "1" is always understood, so even if you type it in, Falsebook will just blank that line.
For instance, I am building a 4-wide bridge. Remember, these values or relative to each sign! So for my four-wide bridge, if I place the sign on the second block along the width of the bridge, it will read "[Bridge]/ /2" and on the opposite side it will read "[Bridge]/2/ " ( "/" for linebreaks there).
Feel free to ask any questions if it's not clear.
