Tombstone lifespan after multiple deletions

[David Boxenhorn]

If I delete a row, and later on delete it again, before GCGraceSeconds has
elapsed, does the tombstone live longer?

In other words, if I have the following scenario:

GCGraceSeconds = 10 days
On day 1 I delete a row
On day 5 I delete the row again

Will the tombstone be removed on day 10 or day 15?