The phrase "actually composed of three" is correct and usable in written English.
You can use it when clarifying or explaining the components or elements of something, particularly when emphasizing the number of parts involved.
Example: "The committee is actually composed of three members, each representing a different department."
Alternatives: "made up of three" or "consists of three".
Actually, research from my laboratory indicates that Openness to Experience is actually composed of three dimensions which are conceptually and empirically quite different from each other.
The singer has just introduced his latest band, 3rdeyegirl, seemingly made up of post-apocalyptic female vagabonds dragged in off the streets of Camden, but actually composed of three fierce blues-rockers and a bald bloke on cowbell.
The calculation is based on the fact that a glycopeptide is actually composed of three parts, i.e. the peptide part, the glycan part with sialic acids removed and the released sialic acids.
Most competitive teams are actually composed of three separate teams of players, each of which is rotated onto the field to perform one type of task.
It was observed that the spring-like carbon nano-coils are actually composed of two fused nano-coils.
This camp, which bristles with counter-arguments at the mention of the word "decline," is actually composed of two very different factions.
The mirror is actually composed of nine plasma television screens and while Untitled may look as if it's been around since the days of Capone, it opened less than six months ago.
Once a storehouse for spices and green coffee beans, the monolithic warehouse is actually composed of seven structures, and has load-bearing, two-foot-thick walls of brick masonry and interior walls of fieldstone.
We demonstrate that the main transform boundary representing the continental extension of the Romanche Fracture Zone, is actually composed of two distinct margin segments, i.e., the ENE WSW trending sheared margin segment of the Cote d'Ivoire-Ghana Ridge and the NE SW trending rift-influenced sheared margin segment of the Ghana Platform.
It is actually composed of two separate courts - the Court of Justice and the General Court.
The horn is actually composed of two parts that grow side by side but do not fuse.
