AT command, "+CMER", I get "+CIEV: 2,3" "+CIEV:2,4" repeat.

Dear All, For AT command,

I input +CMER ( set response keypress) to my device, it response

+CIEV: 2,4

+CIEV: 2,4

..... .... repeat

Why? what's the relation?

Thank you very much.

Boki.