>please help me out here if I am not getting them right.
総検挙件数 = "number of cases arrested"
総検挙人員 = "number of persons arrested"

eg.
1theft case by 3accomplices + 5theft cases by another burglar --->総検挙件数6, 総検挙人員4


By the way, why don't you compare the number of crimes(or crime rates) committed by foreigners in Japan with that of committed by Japanese outside Japan? Is it unfair or illogical to think it from this aspect?

海外邦人援護統計
http://www.mofa.go.jp/mofaj/toko/tokei/engo/