What area does the question mark represent?

It represents area 3 because the fixed clues cover 39 of the 42 cells.

Why is the right edge solved first?

The r4c6=7 clue has only one persistent full-column placement, r1c6:r7c6, and it removes the main overlap from the two 8-cell regions.

The large 6- and 8-cell rectangles overlap several area-correct candidates, so the final bounds matter more than the clue totals alone.

MeowBlock! level guide

hard Target: 7 moves 7 colors

Solve the Hard Level 23 by claiming the seven-cell right edge first, then fitting the two large 8-cell rectangles around it.

Anchor r4c6=7 and drag to r1c6, committing r1c6:r7c6 as a 7x1 rectangle with area 7.
Anchor r3c5=6 and drag to r1c4, committing r1c4:r3c5 as a 3x2 rectangle with area 6.
Anchor r6c5=8 and drag to r4c4, committing r4c4:r7c5 as a 4x2 rectangle with area 8.
Anchor r7c2=6 and drag to r6c1, committing r6c1:r7c3 as a 2x3 rectangle with area 6.
Anchor r3c2=8 and drag to r2c1, committing r2c1:r5c2 as a 4x2 rectangle with area 8.
Anchor r3c3=4 and drag to r2c3, committing r2c3:r5c3 as a 4x1 rectangle with area 4.
Anchor r1c2=? and drag to r1c1, committing r1c1:r1c3 as a 1x3 rectangle with area 3.

Colors in this level:

Violet, Yellow, Green, Blue, Orange, Pink, Purple

Do not release r6c5=8 as r5c5:r7c6; that preview is only 6 cells and blocks the r4c6=7 strip.
Do not move the right 7-cell strip away from column 6; its full bounds are r1c6:r7c6.
Do not merge the two 8-cell regions; the left one is r2c1:r5c2 and the lower-right one is r4c4:r7c5.

Board notes 5 details

Layout: Full 7-row by 6-column board with 42 playable cells. Clues: r1c2=?, r3c2=8, r3c3=4, r3c5=6, r4c6=7, r6c5=8, r7c2=6.
Goal: Partition all 42 cells into seven rectangles. The fixed clues total 39, so r1c2=? resolves to area 3 at r1c1:r1c3.
Opening: Ignore the provisional r5c5:r7c6 preview under the 8 clue. The first persistent placement is r4c6=7 -> r1c6:r7c6, followed by r3c5=6 -> r1c4:r3c5 and r6c5=8 -> r4c4:r7c5.
Danger Zone: The r5c5:r7c6 preview covers only six cells for an 8 clue and consumes the far-right column required by the 7-cell strip.
Mechanics: The Hard board uses one unknown area and several large rectangles. The unknown is inferred as 3, but every committed region must still be rectangular and cover each cell exactly once.

What area does the question mark represent?
It represents area 3 because the fixed clues cover 39 of the 42 cells.
Why is the right edge solved first?
The r4c6=7 clue has only one persistent full-column placement, r1c6:r7c6, and it removes the main overlap from the two 8-cell regions.
What makes Level 23 Hard?
The large 6- and 8-cell rectangles overlap several area-correct candidates, so the final bounds matter more than the clue totals alone.