This value of _pdbx_ligscreen_investigation_screening_exp.result_id identifiers a specific data result record,
for a given experiment, in the pdbx_ligscreen_investigation_screening_exp category.
For example if a fragment is observed in the same experiment / structure to have binding in different places
('On-site binding') and partial-hit ('Off-site binding') there would be a result_id = 1 and result_id = 2.