Less, I also have this but with different numbers. The simplified answer is that the transfer speed that you are seeing isn't the actual speed that it is transferring to the disk in the first place. Instead it is the speed of it being cached into ram, before tapering off to actual write speeds. The defaults work on most machine, but there isn't a one size fits all value. You may find that playing around with those numbers causes more stable write speeds because it will force the system to actually write the data to the usb stick instead of letting large amounts of data cache into ram before actually writing it out to disk. This is often the reason why when it says it is done writing it isn't actually done writing and you have to wait some minutes on some systems to be able to eject. In fact, a lot of times on machines that experience this problem. Hitting the safely eject button is what forces it to immediately write all data to disk.

I believe there was an article about it that I can't seem to recall the name of, but I believe it was something along the lines of "your operating system is lying to you" or something like that.