That appears to be a notation added by the publisher. You should find an explanation of the notation in the Preface or Introduction to the Bible.
The notation may indicate that the spelling of the name in question is a transliteration from the Greek. For example, in the "Old Testament" of most English Bibles, the name of the builder of the ark is spelled "Noah", which is a transliteration from the Masoretic Hebrew. But in the "New Testament", the name is spelled "Noe", which is a transliteration from the Greek. Likewise, "Joshuah" in the OT corresponds to "Jesus" in the Greek.
Each publisher has his own system of annotation. For further assistance regarding this matter, you need to specify the publisher and the edition of the Bible.