What the subdeacon represents
One subdeacon serves, because the entirety of Scripture teaches this sacrament. He is served by one acolyte, because only in the unity of the Church is this sacrament confected.
Quid subdiaconus designat
Unus subdiaconus servit, quia universitas Scripturae hoc sacramentum docuit. Ab uno acolytho servitur, quia in unitate tantum Ecclesiae hoc sacramentum conficitur.
What the acolytes represent
The acolytes hold their candles until the Kyrie eleyson because doctors, the enlighteners of the Church, must proffer light to the faithful by word and example, until the faithful themselves might begin to invoke the Lord by their conduct and might know that Christ, the true light, enlightens every soul.
The seven candles are the seven gifts of the Holy Ghost. The candle that stands in the middle is Christ. Then the candles are arranged in order towards the bishop, for the seven gifts of the Holy Ghost are distributed through Christ to the Church.
The acolyte who carries the thurible represents Joseph, who carried Christ around everywhere; it also signifies the Apostle Paul, who by preaching bore the odour of Christ throughout the whole world.
It is not permitted that six, four, or two acolytes serve, for an even number can be divided, and the Church must not be split, and therefore ‘an odd number is God’s delight’ (Virg., Eclog. VIII, 75).
Quid acolythi designant
Acolythi usque ad Kyrie eleyson lumina tenent, quia doctores, illuminatores Ecclesiae, verbo et exemplo lumen fidelibus praebere debent, quoadusque ipsi Dominum moribus invocare incipiant, et Christum veram lucem omnem animam illuminare cognoscant. Septem cerei sunt septem dona spiritus sancti. Cereus in medio stans est Christus. Deinde luminaria ordinatim versus episcopum disponuntur; quia septem dona Spiritus sancti per Christum Ecclesiae distribuuntur. Acolythus, qui fert thuribulum, designat Ioseph qui undique circumtulit Christum: significat etiam Paulum apostolum, qui praedicando Christi odorem portavit per totum mundum. Sex, vel quatuor, vel duobus ministrare non licet, quia par numerus dividi potest, et Ecclesia scindi non debet, et ideo numero Deus impare gaudet.