They're trying to help you >_<
SL4 SR is worth 140 points, SL5 SR is worth 175 points. R is 10 points.
It takes 4 rares to get an SL4 to SL5. You gain 35 points from that, but if you just used the 4 rares directly in enhancing you would gain 40 points. That's why levelling SR fodder past 4 is a waste - you would get more points from just using those rares on the weapon you're trying to raise.