TDS = (SG -1) 1.1x10 6 ?????

[NMLS]

If my SG is 0.0005 the TDS = (0.0005 -1)1.1x10 to the power of 6 = -109945 ppm . That's obviously not correct. The only way I can get the correct answer is if I remove the -1 and then change the 1.1 to 1.0x10 to the power of 6. So,

TDS = SG x 1.0X10 to the power of 6
= 0.0005(1.0 x 10 to the 6)
= 500 ppm

What's going on with this formula, why does everyone state is as I had written is the first case?

Thanks for all the input!

 

[kenvlach]

Your SG is 1.0005
TDS in ppm = (1.0005 -1) x 1.1 x10⁶
= 550 ppm