if you want to extract last five characters of that cell which exactly
contains twenty characters then use the following function (if your
data starts from A1 downwards) put in B1
=IF(LEN(A1)=20,RIGHT(A1,5),"")
this will return last five characters if the cell contains exactly 20
characters in it otherwise it will return blank cell.
if you want to extract last five characters regardless of the number of
characters in the cell then use the following fuctions.
=RIGHT(A1,5)
hope this could serve your purpose.