From how Clay + HubSpot typically behaves, it won’t blindly create duplicates. If the company gets created on the first run and you rerun the table, Clay will usually match against the existing company (domain / unique identifier) and skip creating it again, assuming the same identifiers are used.
Duplicates usually only happen if the identifiers change between runs (e.g., different domains, missing domain on one run, or multiple “create company” steps without a match condition).