Complex sentence: As design improvements occur, later versions are identified by a change in the number (for example, A3) for minor design changes and by a change to the letter and number for more extensive design changes (for example, B2).
Split into simpler sentences: As design improvements occur, later versions are identified by changes in the letter and number. Changes in the number (for example, A3) indicate minor design changes, whilst changes to both the letter and number are made following more extensive changes (for example, B2).