The available butter record is a source recipe measure for unsalted American-style butter. It does not independently establish physical densities for solid, softened, whipped, and melted butter.
Read the source equivalents together
The reference provides a source-spoon amount and an equivalent source-cup amount. These are linked recipe measures from the same source, not proof that either has an established millilitre capacity.
Use the selected relationship within its stated source measures. A physical-volume conversion needs a separate, appropriate measurement instead of an assumed density for all butter states.
Use a known package weight
If the recipe or package gives the weight you need, enter it directly. A known fraction of that mass can be scaled without converting through a cup.
When the recipe says a fraction of a stick or package, retain the package size in the note. Do not assume a package size merely from the word “stick” or from the place where you found the recipe.
Keep preparation after the amount
Words such as softened or melted remain useful method information even when the amount is in grams. Keep them with the row when scaling or printing.
Butter remains its own ingredient in a baker’s formula. Its entire mass should not be counted as water, and a quantity conversion does not establish a substitution for oil or another fat.