Current VO2 Max doesn't match 4w chart

Garmin Connect shows my current running VO2 Max is 47 but the green line on the 4w chart shows 49. Am I reading it wrong or is this a defect?

 

The 6m and 12m charts do show 47. It's only the 4w chart that doesn't match.

All activities were recorded using a Forerunner 935 with the latest firmware if that matters. The app is Garmin Connect version 4.19.1 for Android running on a Samsung Galaxy Note9.