incorrect CI data?

[mkbane]

please compare this CATS output:

55142816@morgan ~$ local/cats/bin/cats -d 30 --loc M13

The.____ ..... __ .... ________ . _...
.. / )...../ ....( _).) )....
..| /......./ ......| |...( (........
..| |limate./ () \ware.| |ask._ \cheduler
..| _...| __ |....| |....) )....
...\ )..| (..) |....| |...( (..

WARNING:root:config file not found
WARNING:root:Unspecified carbon intensity forecast service, using carbonintensity.org.uk

Best job start time = 2025-03-10 16:24:22.412805+00:00
Carbon intensity if job started now = 22.07 gCO2eq/kWh
Carbon intensity at optimal time = 22.07 gCO2eq/kWh

with the data downloaded from carbonintensity.org (see screenshot)

If the values for 16:00-16:30, 16:30-17:00 are 20 and 22 g CO2e/kWh then how can the CI be higher than 22 g if the job starts before 16:30?