## Explanation

The formula first uses the ISNUMBER function to test if the value is a number, and applies a simple logical if so:

```
=IF(ISNUMBER(B4)
```

For any number less than the value in "input", the formula will return TRUE and the conditional formatting will be applied.

However, if the value is not a number, the formula then checks if the first character is a less than symbol (<) using the LEFT function:

```
IF(LEFT(B4)="<"
```

If so, the MID function is used to extract everything after the symbol:

```
MID(B4,2,LEN(B4)
```

Technically, the LEN function returns a number 1 greater than we need, since it includes the "<" symbol as well. If this bothers you, feel free to subtract 1.

The result of MID is always text so the formula adds zero to force a Excel to convert the text to a number. This number is then compared to the value from "input".