"Perhitungan sudut persegi ini sudah benar."

Translation: The calculation of this square's angles is already correct.

[JamesTWils]

Not much to calculate in the angles of a square. The corners are 90 degrees and the diagonals are 45 degrees, or else it is not a square.

[jmaddz]

That's why it's already correct.

[donny309620]

I would translate the meaning this way: "The calculation of the angles of this square is correct." Also, the word "already" is redundant in the English sentence.

[joeldipops]

It's not redundant. It adds emphasis, you just have to make up a context.

Student: "I'm trying to figure out the answer but I don't think I have this calculation right"
Teacher: "Well the calculation of the angles is already correct, so just move on to the next question"

[jmaddz]

I thoughy the word for "correct" was "betul" as opppsed to "right" meaning "benar"... bukan?

[Annita1980]

Can use both words