Warning: "Increasing burst size for interface <if-name> from <X> to smallest supported value of <Y> bytes"
You tried to configure a burst size for a QoS policy that is less than the interface's MTU size. To ensure correct operation, the system automatically adjusted the value that you tried to configure.
The burst size must be at least equal to the interface's MTU size. If the burst size is smaller than the interface's MTU, the system would not be able to send an MTU sized packet.
You will trigger this warning if you combine commands like these:
set policy qos name <policy-name> shaper burst <X> set interfaces dataplane <interface-name> policy qos <policy-name> set interface dataplane <interface-name> mtu <Y>