"All first sounds" indicates to the teacher that all the phonograms in this word are saying their first/most common sounds. (For example, the phonogram A has three sounds, the first sound is the short A sound.) This means that these spellings do not need to be marked in any way, since they are easy to understand.
Most spelling words in the earliest Foundations and Essentials lessons use their first sounds only and do not need to be marked. Gradually, as more multi-letter phonograms are introduced and students learn words where phonograms are saying a sound besides their first sounds, students will mark more and more aspects of the word to help them analyze its spelling.
Why do you mark them this way?
When Logic of English students learn phonograms, they memorize their sounds in order of frequency. This means that the first sound of each phonogram is the most common.
With single-letter vowels, the first sound is the short sound, and a single-letter vowel always says its short sound unless something in its position or relationship to other phonograms in the word causes it to say one of its other sounds. So when a vowel says its short sound, it does not need to be marked. Students learn rules about what can cause vowels to say their other sounds over the course of the lessons, and they then begin marking the vowels to indicate when they say one of their less common sounds. Until students learn about using the other sounds of a the single-vowel phonograms, the spelling lists only include words that use the first sound.
When are these markings used?
In Spelling Analysis, students and teachers discuss the phonograms and why they are saying what they are saying in particular words. As they do this, they mark each multi-letter phonogram, as well as each phonogram that is saying one of its less common sounds. Eventually they will learn markings for silent letters, advanced phonograms, and exceptions to the rules.
A detailed guide to the process of dictating and analyzing spelling words can be found in the introduction to Essentials. In Foundations, the steps are modeled in the lesson script in various lessons. You can also see the steps outlined on the Spelling Analysis Card, or explained in detail on our blog: Free Spelling Analysis Tutorial.
You can also learn more about spelling analysis with one of our video Mini-Courses!