Sig Figs involving pH

[Daniel23]

My TA discusses how the significant figures only count for the number behind the decimal point and not before the decimal point when dealing with pOH and pH. Why is this so? An example problem is: pOH= -log(9.7 x 10^-6) = 5.01 (Only 2 sig figs, not 3). Then pH= 8.99 (Again, only 2 sig figs, not 3).

[Chem_Mod]

To clarify, this is due to the nature of the logarithmic operation in math. If you take the log of a number, the answer will have as many digits after the decimal as there were significant figures in the entire number you started with. If you take the antilog of a number, you must express the answer with only as many significant figures as there were after the decimal in the number you started with.