What is the significance of '2/3rd' as Raghav & 6 other AAP Rajya Sabha MPs merge with BJP?

As per the Anti-Defection Law, if at least 2/3rd members of a legislative party agree to merge with another party, they are exempt from disqualification. AAP has 10 MPs in Rajya Sabha, therefore, Raghav Chadha announcing his and six other AAP MPs' "merger" with BJP is more than 2/3rd. Notably, an individual's defection usually results in the loss of seat.