The short answer is "yes".
Just edit the standard.mdb file and the software will utilize the updated standard composition for all quant calculations.
One note however... recently I started saving the standard compositions in each probe MDB database. Why? Just in case someone sends me an MDB file, and the same standards aren't present in my local standard database, the application can now create a "temporary" standard database for looking probe data from other labs. See this post here:
http://probesoftware.com/smf/index.php?topic=42.msg934#msg934So what that means is that when you edit the standard composition in the standard.mdb file, and re-open your probe database, the program will note that there is a change in the compositions and will ask you which one to update.
In your case you would say"yes" to update the internally stored standard compositions in your probe database.
By the way, after you fix your magnetite composition in your standard.mdb file, it should look something like this:St 395 Magnetite U.C. #3380
TakeOff = 40.0 KiloVolt = 15.0 Density = 5.200
Port Henry, NY
FeO=30.93% (ISE Carmichael)
Fe2O3=68.85%, FeO=30.92% (as FeO=92.73% + 6.90% O)
(Total FeO=92.73%, by EPMA, JJD)
Oxide and Elemental Composition
Average Total Oxygen: 27.803 Average Total Weight%: 100.229
Average Calculated Oxygen: 20.904 Average Atomic Number: 20.970
Average Excess Oxygen: 6.899 Average Atomic Weight: 32.969
ELEM: FeO Al2O3 TiO2 MgO MnO Cr2O3 CaO SiO2 O
XRAY: ka ka ka ka ka ka ka ka ka
OXWT: 92.731 .380 .020 .119 .070 .010 .000 .000 6.899
ELWT: 72.080 .201 .012 .072 .054 .007 .000 .000 27.803
KFAC: .6779 .0011 .0001 .0003 .0005 .0001 .0000 .0000 .1954
ZCOR: 1.0632 1.7784 .9578 2.2899 1.0822 .8056 .9908 1.4163 1.4231
AT% : 42.454 .245 .008 .097 .032 .004 .000 .000 57.158
24 O: 17.826 .103 .003 .041 .014 .002 .000 .000 24.000
Or like this if one assumes stoichiometry:St 31 Fe3O4
TakeOff = 40.0 KiloVolt = 15.0 Density = 5.000
Assumed Stoichiometric
Oxide and Elemental Composition
Average Total Oxygen: 27.641 Average Total Weight%: 100.000
Average Calculated Oxygen: 20.731 Average Atomic Number: 21.025
Average Excess Oxygen: 6.910 Average Atomic Weight: 33.077
ELEM: FeO O
XRAY: ka ka
OXWT: 93.090 6.910
ELWT: 72.359 27.641
KFAC: .6810 .1946
ZCOR: 1.0626 1.4207
AT% : 42.857 57.143
24 O: 18.000 24.000