Convert an array of characters to float

I have got a problem with my funtion to convert an array to float. I use the "Debug" to see the value of my variables. The problem is in the multiplication on the second element of array fd[1] only when there is a "7","8" or "9", for example to convert "070000" the value of bux=4464, for others value the funtion works perfectly.

float Conv_C2F_FE(unsigned char fd[6])
{float bux;
 bux=(fd[0]-0x30)*100000;
 bux=bux+(fd[1]-0x30)*10000;
 bux=bux+(fd[2]-0x30)*1000;
 bux=bux+(fd[3]-0x30)*100;
 bux=bux+(fd[4]-0x30)*10;
 bux=bux+(fd[5]-0x30);
 return bux;
}