The shortcut "Alt+=" is to AutoSum the numbers that are adjacent in the same row or column. The shortcut will sum only the adjacent numbers. Please see below for details or check more data functions.
Step 1: Click any cell after the data, but normally the cell right after the data (or the cell below the last data cell if you are calculating the numbers in a column);
Step 2: Press and hold the key "Alt" from the keyboard, and click the key "=";
Step 3: Press the "Enter" key from the keyboard and you get the result.
Alternatively, you can always use the commands from the ribbon.
Step 1: Click the cell after the data row;
Step 2: Click the "Home" tab from the ribbon;
Step 3: Click the "Autosum" in the "Editing" section from the ribbon;
Step 4: Press the "Enter" key from the keyboard to have the result.