It can show up as either depending on whether there is any chlorine in the water sample. There are two possibilities:
Chlorine in water ---> DPD dye turns pink ---> FAS drops added but react with MPS ---> result is that MPS gets recorded as part of FC
No chlorine in water ---> DPD dye remains clear ---> R-0003 added, reacts with MPS, and sample turns pink ---> FAS drops added to turn to clear ---> result is that MPS gets recorded as CC
Basically, MPS doesn't react directly with DPD (at least not noticeably enough to produce a color) except at higher MPS concentrations. However, it does react with the FAS drops used for titrating FC and it reacts with the R-0003 potassium iodide used in the CC part of the test. However, if the MPS reacts with FAS during the FC part of the test, it only gets recorded there since there will be none left during the CC part of the test.
In a regular DPD (not FAS-DPD) chlorine test, the MPS shows up as CC (unless the MPS is at very high concentrations):
Chlorine or no Chlorine ---> DPD dye turns pink or stays clear ---> R-0003 added, reacts with MPS, and sample turns pink ---> result is that MPS gets recorded in TC (so as CC=TC-FC)
