The point here is that the Punnett Square just gives us all the possible combinations for two sets of objects / phrases / conditions / whatever. You list one complete set along the top, and the other complete set across the side.
Of course it’s possible that the two sets might have some elements in common. For example, when I go to the Chez Punnett, I may not care what twp dishes I eat instead I might just care what they cost. So my square might look like this:
| $24 (Shrimp) |
$24 (Trout) |
$28 (Gratin) |
$28 (Turkey) |
$37 (Hen) |
|
|---|---|---|---|---|---|
| $13 (Choc Mink) |
$37 | $37 | $41 | $41 | $50 |
| $13 (Choc Cake) |
$37 | $37 | $41 | $41 | $50 |
| $17 (Popsicle) |
$41 | $41 | $45 | $45 | $54 |
| $17 (Gelato) |
$41 | $41 | $45 | $45 | $54 |
| $17 (Croissant) |
$41 | $41 | $45 | $45 | $54 |
Notice that many meals cost the same amount when tallied up.