Think of it as "parsing instructions". If you know the form of the string that you want to parse (in this case it is always the word "Tank " followed by a number) you can tell it to output specific parts of the string and handle some of the datatype conversions at the same time.
Note that if the input string does not match the parsing instructions the function will throw an error so in general you should account for that and be able to handle the outputs not being populated properly. I got lazy in the VI I sent you but if you added another control called "tank 5" (and added it to the Event) the scan from string would cause an unhadled error.
