Bordas aplicadas às células também se aplicam à (s) célula (s) adjacente (s). Por Microsoft KB on Borders (2007) -
NOTE
If you apply a border to a selected cell, the border is also applied to adjacent cells that share a bordered cell boundary. For example, if you apply a box border to enclose the range B1:C5, the cells D1:D5 acquire a left border.
If you apply two different types of borders to a shared cell boundary, the most recently applied border is displayed.