If you do not want to run a cron-job, you can switch the small top-blocks to display only the current high-lows.
# $my_choice = 'multi'; // day / month / year
Set line 4 in the small blocks to comment
If you want to have multiple high-lows you need to run a cron-job to calculate the high-lows for day month year a.s.o.
Explained here No High/Lows, where is history and graphs data used for, and ? cron ? in the middle Missing High-Low values solution
Wim