Please help

My question is about z scores. To calculate probablity in a normal distribution, where we know mean and standard deviation we calculate z and then check score. the scores are always given 'upper' and 'lower'. What does that mean? When should one check 'upper' and when 'lower'. My idea is if the question is being asked 'what is the probablity of getting more than n value' then we will check upper value and if the question is ' what is the probablityof getting less than n value' then we will check lower score of z.

Can someone clarify it to me?