[LARTC] HTB not working quite the way I'd expect?

[tack@xxxxxx (Jason Tackaberry)]

(tc output below cropped)
> class htb 1:11 parent 1:1 leaf 8066: prio 3 rate 400Kbit ceil
>   1600Kbit burst 2Kb/8 mpu 0b cburst 3647b/8 mpu 0b quantum 5120 ]
>   level 0
>  rate 192901bps 236pps backlog 36p 
> 
> class htb 1:1 root prio 0 rate 2000Kbit ceil 2000Kbit burst 4159b/8
>    mpu 0b cburst 4159b/8 mpu 0b quantum 25600 level 3 
>  rate 191724bps 239pps 
> 
> class htb 1:10 parent 1:1 leaf 8065: prio 1 rate 1600Kbit ceil
>   2000Kbit burst 10Kb/8 mpu 0b cburst 4159b/8 mpu 0b quantum 20480 
>   level 0 
>  rate 1380bps 9pps 

Now that I study this a bit more, how can it be that the parent class,
1:1, has a rate that is LESS than the sum of its children's rates? 
Either I've uncovered a bug, or I'm greatly misunderstanding something.
;)

Jason.