RINNAI Water Heater Flush Procedure

I want to flush my tankless water heater (DIY).

I've never read plumbing schematics before.

Which one of these is the "V1" value they are referring to in the doc?

(And have I correctly identified all the values??)

P.S. The values I circled look like threaded ports, but the diagram leads me to believe V1 is to to the left.

EDIT:

EDIT2: This is how I flushed it and it worked!