Hi Hari for one fifth and one seventh, you measure from centre of speakers to side wall and for one third you measure from inside of speaker to side wall.
So your speakers are set up using one fifth principle from side wall
Hi fiftyfifty, the one third principle has nothing to do with the speakers. It has to do with how room nodes interact. Room node interaction is supposedly lowest at one third of side wall distance between the centre of speakers. But this is not practical. So next best is one third between the insides. Then one fifth between centre of speakers. And so on. Depending on driver dispersion, you may need to add some treatment.
The quarter wave principle is one of the techniques studio engineers use to determine studio treatment. Typically they use a combination of monitors and big 18 inchers. If monitor cut off is 50 hz, they will see if they can place it at 94 inches from front wall. If yes, the 18 inchers will be placed flushed on the front wall so that it acts like an infinite baffle. If such distances are not possible, then depending on where the monitor is placed, they will know what frequency they need to absorb. This is the normally the first step towards figuring out what treatment to do for a studio.
There are other ways of approaching speaker placement, but I find above a very good start point
To further add to above, since my speaker is 94 inches from front wall, I have taken care upto 50 hz. For below 50 hz, I will technically need to have absorbers on the front wall. I will need to have a specially made absorber for this. I cannot use a broad band absorber since most of the problems are taken care of using quarter wave. Use of absorbers for below 50 hz will further improve the sound in my room, but I let it go since it’s not practical