ah sorry about that, hmm looks like it's not behaving like how we both think it should work.
I just tested it out and when you enter in within the last 30 days it automatically switches it to 1 month. It also returned a record dated 1/15/2018. So sounds like it there is no difference in how the filter is applied, which is unfortunate because that is exactly how it should work...
Seems like the best bet is to do a filter between the desired date/times.