How to extend the counter-part sign? What even is this? As I'm learning to master the first jhana one must do two things, master the five masteries &amp; be able to extend the sign. For the masteries,

• Mastety Of Adverting
 ×Turning your attention &amp; focus on any jhana factor after! anywhere,time or place

• Mastery Of Attainment
  × Entering jhana concentration quickly, Anytime you wish 

• Mastery of Resolving
×Staying in the absorption for as long as one wants. 

• Mastery of Emerging
× Emerge from The Jhanas Quickly

• Mastery Of Reflection
×Looking at &amp; learn each thing you did to enter each jhana factor.

Please tell me if I'm incorrect. Now for extending the sign. I don't truly understand how to do such a thing, or even what it is. Here's a passage from the book I'm reading.


  The perfecting of the first jhana involves two steps: the extension of the sign 
  and the achievement of the five masteries. The extension of the sign means 
  extending the size of the counterpart sign, the object of the jhana. Beginning 
  with a small area, the size of one or two fingers, the meditator gradually 
  learns to broaden the sign until the mental image can be made to cover the 
  world-sphere or even beyond (Vism. 152-53; PP.158-59).


Can someone please elaborate for me please. I need to understands what the counter-part sign is &amp; how to extend it. Is it a mental image you have? So a kasina ot any other mental image you form?
From my own meditation experience... For what it's worth...

Usually, when meditation is going well, you feel very comfortable and can relax, your level of concentration grows. Concentration on what? On nothing really, just on sitting and being in the moment. At some point even the breath stops being important, it's more like you no longer get distracted from sitting and staring at your own "raw" mind...

When that happens, it feels almost like you start tripping. I'm sorry for using a highly contemporary comparison, but I can't come up with a better image for what happens at that moment. At least in my experience, I start floating into some altered state of mind... While staying firmly in the present moment, without losing my concentration... In this state of mind I "see" feelings as "shapes" and "colors". It's hard to describe, because that "seeing" is not really visual, the shapes are not really shapes and the colors are not colors. They are feelings. But they are much more "loud" and "thick" than our normal feelings, they have more structure and differentiation so to speak. I believe this is the so-called "counterpart sign".

No two people have the same experiences, but when your get in touch with your deep subconscious emotional mind, you will experience something strange. This something, whatever it is in your case, will start small and then grow and expand. Then you have a choice to either keep relaxing and going deeper into that, or hold on, or come back out. In my experience, when I go deeper I eventually fall into something like a dream state.

In this dream state I lose sense of time, and I don't really have control, but there is still a sense of something going on, and I feel that, and it is good. Sometimes there is a feeling of some mental knots getting untied. Sometimes there is a feeling of resting. Sometimes there is a feeling of opening. Sometimes there is a feeling of sweetness. It also serves as a kind of reset button, meaning, when you "wake up" you feel much refreshed, more grounded, well-rested, balanced, and calm.

It's not really that magical. It's rather similar to a moment when you're falling asleep.

So my answer to your question, "how to extend the counterpart sign" is: "by relaxing into it, by relaxing deeeeep into the present moment".