finite state machine – oval of FSM diagram represent what?

I am reading a document of varnish, and I get the important VCL state image:

we know we often use UML as standard to draw state machine.

but the svg image not, is it follow another standard? or not?

I can understand the start/end diagram (hexagon), state diagram(two rectangle), judgement condition(rhombus) ,

but I don’t understand the oval represent what, please tell me.