GPT-5.5 vs GPT-5.6 Luna for spreadsheets & Excel

Faults:

1. **`VLOOKUP` column index is invalid**  
   `Sheet2!A:D` has only **4 columns**, so `VLOOKUP(...,5,...)` is impossible. The largest valid column index is `4`.

2. **The date criterion should be parenthesized for clarity**  
   Use `">" & (TODAY()-30)`.

Corrected formula:

```excel
=SUMIF(A:A,">"&(TODAY()-30),B:B)+VLOOKUP(C1,Sheet2!A:D,4,FALSE)
```

If you truly need the 5th column, then the lookup range would have to include column E, e.g. `Sheet2!A:E`, but you said Sheet2 only has columns A to D, so `4` is the correct maximum colum…

The fault is in the `VLOOKUP`:

- `Sheet2!A:D` contains **four columns**, but the formula requests column **5**.
- If the intended return column is D, the column index must be `4`.
- The value returned by `VLOOKUP` must also be numeric because it is being added to the `SUMIF` result. If column D contains text, convert it to a number or correct the source data.

Assuming the lookup value is in column A and the desired result is in column D, use:

```excel
=SUMIF(A:A,">"&TODAY()-30,B:B)+VLOOKUP(C1,Sheet2!A:D,4,FALSE)
```

If you actually intended…