with +/- means that the gpa calculation is based on what the actual grade was...e.g. A-, B+, C-, etc
without it means that your A- would be counted as an A, B+ as a B, etc
Since your gpa with +/- is lower, it seems like you had more - letter grades (A- vs. A+). w/o tends to be helpful for those who have more - than those who have + (because it brings down the gpa for people with +)