I've alignment using Tophat2, and got ".bed"files, including deletions.bed, insertion.bed, junctions.bed and I opened the "deletions.bed" file. There are 4 columns

track name=deletions description="TopHat deletions"
chr1  16917    16919   -   1
chr1  18869    18871   -   3
chr1   24347    24349  -   3

What is in the 4th and 5th columns? I don't know that means.

I think 1st column is chromosome, 2nd & 3rd column means where the deletion takes place, 4th is I don't know, 5th is how many deletions?

3rd - 2nd != 5th

Please help