Ghufranak.
I ask for Your forgiveness.
Meaning and reference
Sunan Abi Dawud 30 reports the selected word after the Prophet left the place used for relieving himself. Sunnah.com attributes a Sahih assessment to Al-Albani.
The Arabic is brief, but its meaning is a real request for forgiveness. Avoid adding a long explanation of why it is said as though that explanation were quoted in the report; scholarly explanations and the transmitted wording are different kinds of information.
Remembering the correct occasion
Learn the entry and exit texts as a pair of different actions: seeking refuge before entry, then asking forgiveness after leaving. The pair is useful for remembering the routine, not evidence of an extra combined recitation.
Questions about speaking inside, modern bathroom layouts or purification belong to their own etiquette guidance. The short exit report does not settle all of those issues.
Teaching a beginner
Explain the meaning in ordinary language and practise the pronunciation once it has been checked. A simple reminder can help someone learning a daily routine without making them anxious about occasional forgetfulness.
Respect privacy and avoid putting sacred text in an unsuitable place. A household reminder should assist learning, rather than become a required object or a source of arguments.
Common questions
Is it the same as the entry prayer? No; the meanings and references differ. Why is it so short? A meaningful supplication need not be lengthy. Does the report explain every reason for saying it? No; distinguish the quotation from later commentary. Must it be repeated a certain number? This card does not establish a repetition count.