the + n will allow you to match your actual hyperspeed to that of people you're flying with (but can't put into a squadron), e.g. since your piloting level is higher than that of your friend, but you still want to arrive at approximately the same time, you set your hyperspeed to 5.8 while he sets his to 6.0. Due to your higher piloting skill, your 5.8 speed will still make you about as fast as his 6.0 speed and you will arrive at the same time.

(note, the numbers above are just figures of my imagination, you'll have to do some tests to find out which numbers will work best for you).