To give you credit for the remainder thrown away by this rounding (0.2 in the example, in general a number between -0.5 and +0.5), this remainder is in turn rounded to the nearest multiple of 1/3. If this is +1/3 (as in the example) you get a "+" suffix, if it is -1/3 you get a "-", and if it zero you get no suffix on your letter grade.
This becomes a bit complicated when you make a table, because 1/3 does not have a simple decimal representation. But here goes:
| Letter grade |
Minimum numerical grade |
Maximum numerical grade |
|---|---|---|
| A+ | 4.167 | none |
| A | 3.833 | 4.167 |
| A- | 3.5 | 3.833 |
| B+ | 3.167 | 3.5 |
| B | 2.833 | 3.167 |
| B- | 2.5 | 2.833 |
| C+ | 2.167 | 2.5 |
| C | 1.833 | 2.167 |
| C- | 1.5 | 1.833 |
| D+ | 1.167 | 1.5 |
| D | 0.833 | 1.167 |
| D- | 0.5 | 0.833 |
| F | none | 0.5 |