VO2max decreasing altough my workouts are showing "VO2max effect"

Hi all, before today workout my VO2max was rated 45 and in the last two workouts the workout benefit was indicated as "VO2max effect".

I had a race this morning, again with "VO2max effect" but the value decreased to 44, anyone can explain why decreased if the benefit was for VO2max?

thanks