Hi,
As explained by others:
No. Characters > Define what the variable can store
Output Length > Describe maximum length with formatting characters
Take a example:
12345678901234567 (No. Characters - 17, Decimal Places - 0,Output Length - 17)
123456789012345.67 (No. Characters - 17, Decimal Places - 2,Output Length - 18)
123,456,789,012,345.67 (No. Characters - 17, Decimal Places - 2,Output Length - 22)
-123,456,789,012,345.67 (No. Characters - 17, Decimal Places - 2,Output Length - 23)
So, with you example:
(1) No. Characters 17 (i.e. Contain up to 17 digit)
(2) Decimal Places 2 (i.e. 2 out of 17 digit is decimal places)
(3) Output Length 23 (i.e. with formatting characters , . - etc... the max length is 23)
Wish it is clear now
Regards
Bill