I'm using SyteLine 5 and i'm cleaning tmp-sum once a year as a part of my year end procedures. And i never had any remorses doing it
If you want to validate the theory without deleting the entire content you could delete the records between 28000 and 32000. Don't forget to take a backup of the table. And yes you must do it when nobody is logged into syteline.
Je serais content de savoir que j'ai aidé quelqu'un!