The distribution of the p-value, given that the null is true, is uniform between 0 and 1. IF the null is true, you're equally likely to get a p-value of 0.01 a

The distribution of the p-value, given that the null is true, is uniform between 0 and 1. IF the null is true, you're equally likely to get a p-value of 0.01 and 0.87.