Embodiments of the invention provide apparatus, systems and methods wherein pre-event and post-event analyte concentration readings associated with an event are collected and processed to determine a numerical delta. The numerical delta may be displayed on a visual display to aid in a ready determination of the affect that the event (alone or in combination with medication and/or insulin dosages) had on the analyte concentration levels. Medication and/or insulin dosages may be displayed alongside the numerical delta to gauge immediate relationships between numerical delta, dosage and/or an associated event. Apparatus and systems for calculating and displaying the numerical delta are described, as are other aspects.