GPT-5.5 vs GPT-5.6 Terrafor 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…

Faults:

1. `VLOOKUP(C1,Sheet2!A:D,5,FALSE)` requests column **5**, but `Sheet2!A:D` contains only **4 columns**.  
   - If the intended return column is `D`, use column index `4`.
   - If a fifth return column is actually needed, the lookup range must extend through column `E`.

2. The date criterion is clearer and safer written with parentheses around the date calculation: `">"&(TODAY()-30)`.

Corrected formula, returning the value from column `D` of Sheet2:

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

If you…