The Biblical predictions refers to the predictions found in Revelation of the reunification of Church and State, specifically in America, in the last days.
Below is what is believed by most Seventh Day Adventists:
In Rev 12:13-16, we see that God's church (the women) was a persecuted church throughout history. She existed through a time where there was no liberty of conscience. She was hidden in the wilderness for "a time, times, and half a time" (Rev 13:14) to save her from being "carried away of the flood" from the dragon (Rev 13:14), until the "earth the helped the women" (Rev 13:16).
Now water in Revelation refers to people "The waters which thou saweth, where the whore sitteth, are peoples, and multitudes, and nations and tongues" (Rev 17:15). Conversely, earth would mean a land relatively uninhabited. The time period, "A time, times and half a time" is 1,260 days (Rev 12:6), and refers to 1260 years if a day in prophetic time equals a year. Combined it depicts: God's church persecuted and hidden for 1,260 years, until the reformation during the later period. A large number of protestants sailed from Europe to a new land, North America, founded on religious liberty.
Next, Revelation 13 describes two beasts, the beast from the sea (Rev 13:1-10) and the beast from the earth (Rev 13:11-17).
The beast from the sea is the persecuting power that rose out of the Roman empire. Those familiar with Daniel 7 would tie the description of the beast in Rev 13:2 to be the cumulation of the empires described in Daniel 7. It is also a religious power as the beast is actively worshipped (Rev 13:4) and speaks blasphemies (Rev 13:5). It rules as a civil power for 42 months, which is the 1,260 year period in History mentioned (Rev 13:5). It made "war with the saints" of God and had civil authority as "power was given him over all kindreds, and tongues, and nations" (Rev 13:12). This is the church of Rome, the Roman Catholic church of the middle ages, which became corrupted from within.
Lastly, we get to the beast from the earth. The earth already points strongly to North America, a land that was relatively uninhabited (Rev 12:16). The beast that comes out of the earth has two horns like a lamb, which points to America's two founding principals as the reason for its power -- civil and religious freedom. However this beast would speak like the dragon, infringing on religious freedom. Revelation predicts that the civil government of the United States reunites with world loving Christian religious leaders, slowly removing the separation of church and state.
Revelation 13:12-14, describes predictions that have not yet happened. Prophecy points to a time when God will allow those working for the dragon to exercise false miracles (Rev 13:13-14), and all who do not have a strong foundation in the Bible will be deceived, no matter the denomination. World loving churches will reunite with the papacy and worship the first beast (Rev 13:12). Rev 13:14 describes a democratic power as it appeals to the people, and the image of the beast is the style of government similar to the first beast that forces religious conscience (Rev 13:15). However, all who love God, of every denomination, will come out of her (Rev 18:4).
Under this environment the worship of God on Sunday becomes a topic of controversy. It is the only law of the ten commandment that was changed by the papacy. The Catholic church said so itself as evidence of its power from God. Efforts will be made by the beast to pass Sunday worship as law, just as in history. Only then does Sunday worship become the mark of the beast as described in Rev 13:15-16.
For further study on this topic, I recommend whole heartily the book "The Great Controversy" by Ellen White (Wikipedia, Amazon, Goodreads), written almost 100 years ago, but even more relevant today.