Adding letters to capacitor values isn't that complicated; it's just one more little detail to be aware of. The following sums up some basic letter codes for capacitor tolerances:
Some capacitors are defined by a three number code followed by a letter. This letter represents the tolerance of the capacitor, meaning how close the actual value of the capacitor can be expected to be to the indicated value of the capacitor. The tolerances are indicated as follows:
Read B as 0.10 percent.
Read C as 0.25 percent.
Read D as 0.5 percent.
Read E as 0.5 percent. This is a duplication of a D code.
Read F as 1 percent.
Read G as 2 percent.
Read H as 3 percent.
Read J as 5 percent.
Read K as 10 percent.
Read M as 20 percent.
Read N as 0.05 percent.
Read P as plus 100 percent to minus 0 percent.
Read Z as plus 80 percent to minus 20 percent.
The above was copied from this site, which adds a little bit more info.
Next week, we'll talk about more naming schemes, and wind up with a couple of links which illustrate just how (unnessarily?) complex this subject can become.