Our responsibility is to chant the prescribed 16 rounds properly. If there is no concentration, then completing 64 rounds or even 108 rounds has little value.
AS We Chant, we are engaging in hrsikena hrsikesa-sevanam service to the Master of the senses with our senses. and the soul will use these senses in the service of Harinama Prabhu, in chanting attentively.