Uh... z sounds right, but the proportion doesn't. For z = 1.88, p = .96995. Think about it - z/t scores represent the # of stdev's out from the mean, and the 68-95-99 rule states p for |z|<2 is ~95%, so it clearly couldn't be just .46995. What you calculated was the proportion from the mean up to 1.88 stdev's out, but you have to add 0.5 for the bottom half of the bell curve (from the mean to -infinity stdev's out).

I hope you figured it out by now though. Good luck.