They've apparently been imported as text strings rather than numbers. To
convert, type a 0 in some empty cell and copy it (ctrl+C). Then select your
imported data and, from the menu bar, Edit > Paste Special, select Values and
Add, then click OK.
you have 3 alternatives:
1) in b1 you put in the formula :=a1+0 then copy down
2) in b1 you put in the formula :=trim(a1) then copy down
3) in b1 you put in the formula :=value(a1) then copy down