in generateBoundingBox function, why plus 1?

[ZhiqiJiang]

in generateBoundingBox function of the file generateBoundingBox.m, there is "boundingbox=[fix((stride*(boundingbox-1)+1)/scale) fix((stride*(boundingbox-1)+cellsize-1+1)/scale) score reg]". Then my question is why plus 1.

Thank you in advance.