All the music theory revision booklets revise information which has already been covered (and practiced) in All-In-One To Grade 5. Exercises test a pupil’s comprehension of more than one topic at once and wording, wherever possible, is the same as that used by the relevant exam board so that students will feel well prepared and confident in the final stages before an exam.
In Grade 3 there are more key signatures, compound time signatures are revised as well as diatonic intervals (which require that you remember the technical name as well as a number).
The short four page appendix contains topics which are beyond ABRSM grade 3 requirements and specifically intended for Trinity College London grade 3 students (real and tonal sequences, broken chords, chord inversions: root, first and second, writing 4-part tonic chords for SATB in root position, primary chords, adding a bass line to a tune or vice versa, perfect cadence and orchestral instruments).