@SUM(list) adds the values in list .
list can contain any of the following, in any combination: numbers, numeric formulas, and range addresses or range names that contain numbers or formulas. Separate elements of list with argument separators; such as a ; (semicolon).
Text entries in ranges in list do not cause statistical @functions, such as @SUM and @AVG, to evaluate to ERR indicating an error. Your spreadsheet assigns the value 0 to all text labels in list (either in a range or listed individually) and includes them in calculations. For example, if you use @SUM to calculate the sum of the values in a range and the range contains a text entry, your spreadsheet considers the text to have the value 0 when calculating the sum. Your spreadsheet ignores blank cells (cells that contain no data) in multiple-cell ranges in list.
@SUM(B5..B9) returns the sum of the values in B5..B9.
@SUM(SALES;M25..R25) returns the sum of the values in the range SALES and the range M25..R25.