Can you help me understand the standard normal distribution chart?

Can you help me understand the standard normal distribution chart? Please see problem below:An online stock trading company makes part of their revenue from clients when the clients trade stocks therefore, it is important to the company to have an good idea of how many trades its clients are making in a given year. In a sample of 120 clients of an online stock trading company, the average number of trades per year was 82 with a standard deviation of 16. If you were to test the hypothesis that the average number of trades per year is different than the previous year when the average number of trades was 85 (using the 5% level of significance), what is p-value for this test? (please round your answer to 4 decimal places)