Lexographic value
In Excel, the formula
=COMBIN(49,6)-SI(44-C2>0,COMBIN(49-C2,6),0)-SI(45-D2>0,COMBIN(49-D2,5),0)-SI(46-E2>0,COMBIN(49-E2,4),0)-SI(47-F2>0,COMBIN(49-F2,3),0)-SI(48-G2>0,COMBIN(49-G2,2),0)-SI(49-H2>0,COMBIN(49-H2,1),0)
will give you the lexographic value for the 6 numbers placed in cells C2 to H2. Adjust as necessary.
In short, the lexographic value is 1 for numbers 1, 2, 3, 4, 5 and 6 (the first combination) and 13,983,816 for numbers 44, 45, 46, 47, 48 and 49 (the last one) in order.