Missnaming ships?

[Eliza Creststeel]

Ship of the Line was the classification of heavy warship, somewhat generic.

"A ship-of-the-line was a type of naval warship constructed from the 17th century through the mid-19th century, to take part in the naval tactic known as the line of battle, in which two columns of opposing warships would maneuver to bring the greatest weight of broadside guns to bear. Since these engagements were almost invariably won by the heaviest ships carrying the most powerful guns, the natural progression was to build sailing vessels that were the largest and most powerful of their time.

In the 17th century fleets could consist of almost a hundred ships of various sizes, but by the middle of the 18th century, ship-of-the-line design had settled on a few standard types: older two-deckers (i.e., with two complete decks of guns firing through side ports) of 50 guns (which were too weak for the battle-line but could be used to escort convoys), two-deckers of between 64 and 90 guns which formed the main part of the fleet, and larger three- or even four-deckers with 98 to 140 guns which were used as admirals' command ships."

"In naval warfare, the line of battle is a tactic in which the ships of the fleet form a line end to end. " - Both quotes from Wikipedia

So, they can create other vessels beyond the current set without worry. A ship of the line could be of varying sizes.