i've also been studying for the OAT using Kaplan and i've scored 260 and 270 on my last practice tests. i actually took the OAT today and made a 330 in RC. on the opted i scored a 380 on the rc but i think that since there is only one passage, it's not very accurate. don't worry too much though because i scored much lower on all the kaplan practice tests. they make the questions more difficult so that you're able to tackle any problem.
also, it really depends on your technique for tackling the rc. this method may or may not work for you, but i skim the passage, number and jot down what each paragraph discusses so that when i answer the questions, i know which paragraph to look at. it got me a decent grade on the oat. hopefully, this helps! good luck!