As far as I know it works like this:
- Player is killed: This adds one kill. but no death yet.
- Player receives a revive offer: This has no effect on any stats.
From then on there are multiple possibilities:
- Player declines and spawns new: This costs the team one ticket and the player receives one death.
- Player accepts, but is killed: This adds one kill. The player is no longer revivable, unless the last revive happened more than 20 seconds (or 10 seconds?) ago. This has no effect on tickets, but the player receives one death, if he's killed before being able to be revived once more. One ticket is used once he respawns though.
- Player accepts and survives: This has no effect on any stats (although I think your "in one life" stats continue counting).