The x-axis represents days. These charts show the most recent 10 log entries. A point on the chart will only show if there is a log entry for that day. Empty days are skipped.

The y-axis is different for each chart and shows multiple units on a single chart as follows:

Metrics
RHR (Resting Heart Rate) - bpm
Sleep - hrs
BPS - Systolic Blood Pressure - mmHg
BPD - Diastolic Blood Pressure - mmHg
Weight - lbs/kg
Fat - %

Cardio
Duration - minutes
Distance - miles/km
AHR - Average Heart Rate - bpm
MHR - Maximum Heart Rate - bpm
Avg - Average Speed - mph or km/h
Max - Maximum Speed - mph or km/h
Pace - min/mile or min/km

Nutrition
Fat - g
Carbs - g
Protein - g

Calories In/Out
Consumed - kcal
Expended - kcal

As I mentioned, I'll try to clarify this on the homepage charts but also may link each chart to a larger version where everything can be spelled out more clearly.

Trevor Stith
Online Fitness Log