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H0 = 95% of orders filled
Ha = greater than 95% of orders filled
We'll use a z test for a proportion. The critical value for a one tailed alpha 0.025 test is z = 1.96. We'll reject the null hypothesis if our z test statistic is greater than that.
Find the test statistic z:
phat = 485/500 = 0.97
z = (phat-p)/sqrt(p*(1-p)/N)
z = (0.97-0.95)/sqrt(0.95*0.05/500)
z = 2.0519
This is greater than the z value from the table for a one tailed test, with alpha = 0.025 (z = 1.96), so we reject the null hypothesis. We can be reasonably sure that they are exceeding their goal.