On NiLS Global Settings you have an option called "Notification Mode", this option is also available under App Specific Settings in case you want to change it to a specific app.
This option set the way notifications are parsed and displayed on NiLS:
Grouped - on this mode, the notification will appear the same way as they appear on Android notifications bar. for example - when you have multiple emails Android will display it like this:
3 new emails
sender name 1 email subject 1
sender name 2 email subject 2
sender name 3 email subject 3
On Grouped mode, NiLS will display it as is.
Separated - on this mode, NiLS will try to extract separated notifications from a single grouped notifications, so on the previous example will display 3 notifications like those:
sender name 1
email subject 1
sender name 2
email subject 2
sender name 3
email subject 3
On Android 4.3 or later, NiLS will also try to receive additional information from a different notifications channel, so it will have more information than the information that appears on the grouped notification. (e.g. full email body, action buttons, etc...)
Conversation - this mode is available on Android 4.3 or later, on this mode, NiLS will use a different notifications channel to retrieve full conversation content from apps that provided it, like WhatsApp, Telegram and many more apps. on this mode each conversation will appear on its own notification and when the user click on the notification he will see the full conversation in addition to the recent message that appear on the collapsed notification.
When the notification doesn't contains full conversation content, this mode will be look exactly like on Separated mode.