bs-minimal-buffer-name-column

bs-minimal-buffer-name-column is a variable defined in `bs.el'.
Its value is

15

Documentation:
Minimum column width for buffer names.
The column for buffer names has dynamic width. The width depends on
maximal and minimal length of names of buffers to show. The minimal
width is bounded by `bs-minimal-buffer-name-column'.
See also `bs-maximal-buffer-name-column'.

You can customize this variable.