We are making use of the worksheet range. Lets assume that from B1 to B16 it is given the number of locations where the job fair has occurred in 2018. Hence, the above formula. SUM is the aggregate function. and we use the = so that all the aggregate functions are listed in drop down in the cell, and such that we can select the correct aggregate function from the list.
. Plugging in the information gives you 
amperes of current.