Definition (house style)
αρνιον (arnion) is the Greek word for “lamb” used exclusively for the exalted Christ in Rev. Unlike amnos — the sacrificial lamb of John 1:29 — arnion binds the victorious Christ inseparably to his slain state: the standing Lamb bears the marks of his death upon the throne (Rev. 5:6).
Bullinger established that arnion occurs exactly 28 times (4×7) of Christ in Rev. Four (the number of the created order) multiplied by seven (divine completeness) marks for him God’s all-encompassing stamp upon redemption. The one apparent exception — Rev. 13:11, the beast-like false prophet — is an imitation of the true Lamb, not a 29th occurrence of the same title.
Usage per author
Bullinger
Bullinger documents the pattern of arnion as a core illustration of his numerical hermeneutic:
“‘The Lamb,’ a special word αρνιον (arnion) as used of Christ, 28 times (4×7). [Note: The Concordance gives 29; but on examination one of these was found to refer to the Antichrist, Rev. 13:11.]”
[Bullinger, Number in Scripture, Part I, ch. II]
The fact that precisely 4×7 occurrences belong exclusively to Christ establishes for Bullinger the divine significance of the symbol: the Lamb is the Lord of all creation, redeeming it through his blood.
Jones
Jones connects the arnion image in Rev. to the jubilee vision and the two works of Christ. Rev. 5:13-14 is for him the eschatological endpoint of the jubilee:
“And every creature which is in heaven, and on the earth, and under the earth, and such as are in the sea, and all that are in them, heard I saying, Blessing, and honour, and glory, and power, be unto him that sitteth upon the throne, and unto the Lamb for ever and ever.”
[Jones, The Laws of the Second Coming, ch. 3]
The Lamb in Jones is the Restorer who through his death-work (first coming, Passover) opens the jubilee and through his living work (second coming, Tabernacles) completes the reconciliation of all things.