What is MonetaryAmount.plus() used for? Which Kotlin operator to map it to?

Question

I'm using JSR 354 a.k.a JavaMoney, and I don't understand what MonetaryAmount.plus() is supposed to do?

For all implementations of MonetaryAmount I found, it simply returns this. The documentation is not helpful to me:

Returns a {@code MonetaryAmount} whose value is <code>+this</code>, with rounding according to
the context settings.

This is a bit unfortunate when using Kotlin, which has operator overloading for the function plus which maps the operator + onto this function, where as it should map onto add in this case.

This can be fixed:

    operator fun MonetaryAmount.plus(other: MonetaryAmount) = this.add(other)

But I'm not sure onto what operator I should map the plus() function to? UnaryPlus?