Xingxing‘s Astronomical Home: Sextractor

I am trying to using the catalog from SEXTRACTOR to get some information. In the process, I have to analyze the error. Then the question come...

I using the error of magnitude first, and find that the error is under-estimated. It is assuming that the "flux_err << flux".

MAG_ERR= FLUX_ERR /FLUX * 2.5/ln(10)

Then, I tried to using the flux directly, but I find this:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ NUMBER X_IMAGE Y_IMAGE FLUX_ISO FLUXERR_ISO FLUX_ISOCOR
1 3276.88 1658.34 0.011211 4.67943e+15 0.212761 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The FLUX_ISO is 0.011211 while FLUXERR_ISO is 4.67943e+15.
I do not know how to convert this to erg/cm^2/s/A.
PS: