Explanation
The Type Into activity is used to type text into a UI element. The activity has different properties that can be configured to control the input method, the delay between keystrokes, the cursor position, and the text formatting. The Activity Project Settings for UI Automation Modern activities allow you to set the default values for these properties at the project level. However, you can also override these values at the activity level by using the Properties panel. In this case, the Activity Project Settings are set to remove a Single Line in Run mode and Multi Line in Debug mode. This means that when the workflow is executed, the Type Into activity will delete any existing text in the UI element before typing the new text. If the workflow is run in Run mode, only one line of text will be deleted. If the workflow is run in Debug mode, all lines of text will be deleted. (UiPath Studio documentation1) References:
1: Configuring Activity Project Settings - UiPath Studio.