In order to interpret the result of a gcms data you must have at least some information about the nature of the components (name, mol wt etc) within the unknown sample. You may have got a list of probable components (for each RT) and some other details like Mol formula, peak area etc. you have to compare the fragmentation pattern of the unknown with the library spectrum. RSI value may be taken as a reference for the most probable component within the sample but it will not reflect the identity of the unknown sample in all the cases.