Sometimes it's hard to isolate a specific character or group of characters by adjusting a Selector's Start and End properties. This is because these properties use percentages as their values. What percent is the letter u in the word iguana? You may not be sure, but you probably are sure that u is the third character.
To adjust Start and End by character instead of by percent, twirl open a Range Selector in the Timeline, then twirl open Advanced. Select the Index option from the Units property dropdown menu. You can now set the Start and End properties to specific character numbers .
Note that the first character is numbered zero, not one. So in the word iguana, the i is character zero, the g is character 1 and the u is character two.