Quick Answer: When the notes in your imported MIDI file don't start with the first measure, Liquid Notes extends the first chord box to the beginning of the piece which may be cumbersome to work with.
Liquid Notes' chord box extensionWhen you import a MIDI file into Liquid Notes, it runs through Liquid Notes' harmonic analysis engine and gets segmented into different chord boxes. Liquid Notes knows no "empty space" - there have to be chord boxes on the entire time line. So, when your MIDI file contains lots of musical rests (respectively time without MIDI notes), Liquid Notes extends the surrounding chord boxes to encompass the empty space.
In most cases this happens only for a few beats of a measure and is hardly noticeable.
It can happen however that when you export only parts of your MIDI arrangement in your sequencer, it includes the time before the first MIDI regions you export as empty measures in the MIDI file. When you then import the MIDI file into Liquid Notes, it will place the first MIDI events correctly after the included empty measures, but extend the first chord box to the very first measure:
This is probably not the result you expect, and can in extreme cases as the above also be inconvenient to work with.
All you need to do to prevent this from happening is to drag the MIDI regions you want to export to the first measure in your sequencer before you export them as a MIDI file.