Removal of splattered grout, carefully with a wood chisel or a sharp knife. It will come off with some prying.
I prefer to use silicon on the corners of the job since they do tend to slightly move, silicon is for flexibility and grout is for permanently. There are two different applications and areas for each's use.
His/her silicon came up because he/she may have applied it on an area that was wet, or you, not being told may have used the shower within 24 hours of silicon application. It takes a good 24 hours to dry and cure out.