To Enter data in a spreadsheet field, select the required field using the mouse, Tab key, Arrow key or Enter key as appropriate and begin typing.
Excel distinguishes between data (text) such as names and numbers and formulas. Formulas are recognised by Excel with the first character in a cell being either a + or an =. So, entering James 25 leaves James 25 as the visible product of that cell’s editing. Entering 25+13 leaves the visible product as 12+13. This is not a set of numbers Excel can use later in a formula. Excel will treat that data as text.
If the entry in a cell is 25, the visible product is 25 but Excel will presume that this is a formula (or number) and can use that data in other functions. So, if there is a column with three cells of data; 15, James, +25+13, Excel will ignore James when using that datum in a calculation that has included all three cells. So, =Sum(A1:A3) will produce the visible product 40.
Excel does not use trailing zeros beyond the decimal point. So the value 1,000.00 should simply be entered as 1000. There is no need for the comma, decimal place or penny zeros. Entering 1000.50 should be 1000.5.
Historically, it was not possible to have more than 255 characters in a cell which limited the size of formulas Excel could manage. So, attempting to add large numbers of numbers in a single cell could be problematic. To this end, experienced Excel users tend to enter only the data Excel requires. Obviously, this also save time in data entry.