According to UGC Regulations 2018 on plagiarism, Level 3 plagiarism refers to similarities:

Under the UGC Regulations 2018, Level 3 plagiarism means textual similarity above sixty percent.

Below ten percent falls in Level 0, which carries no penalty at all.

The band above ten to thirty percent is a distractor, since Level 1 actually spans above ten to forty percent.

Above forty to sixty percent is Level 2, a serious but not the highest band.

Level 3 is the gravest band and draws the heaviest penalties on the offender.

Similarity up to ten percent is exempted before the graded levels begin.