What algorithm does HTB use to calculate available tokens?

Hi,

I'm trying to understand why I'm seeing less (not more) tokens on a
1Mbits HTB class vs a 100Kbits class:

tc class add dev eth0 parent 1: classid 1:1 htb rate 1Mbit
tc -s -d class show dev eth0
class htb 1:1 root prio 0 quantum 12500 rate 1Mbit ceil 1Mbit
linklayer ethernet burst 1600b/1 mpu 0b cburst 1600b/1 mpu 0b level 0
 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
 lended: 0 borrowed: 0 giants: 0
 tokens: 200000 ctokens: 200000

vs

tc class add dev eth0 parent 1: classid 1:1 htb rate 100kbit
tc -s -d class show dev eth0
class htb 1:1 root prio 0 quantum 1250 rate 100Kbit ceil 100Kbit
linklayer ethernet burst 1600b/1 mpu 0b cburst 1600b/1 mpu 0b level 0
 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
 lended: 0 borrowed: 0 giants: 0
 tokens: 2000000 ctokens: 2000000

Why is there 10 times more tokens available on 100kbits (at the same
burst value)?