lynx Welcome to our forum and thank you for your question!
It means that we do not officially support any USB-C power delivery device that is delivering less than 87W of power.
The device might work fine but we cannot guarantee that. And if it works, it is charging slower than the regular charger.
Some people have reported that a 65W charger is working fine since the latest release, but again, it hasn't been officially confirmed.
Please let me know in case you have any further questions.
Thanks again!