FRTS Tc > 249ms

Has anybody else run into this? I have tried it on several routers ,
different platforms , different IOS. I can't seem to get a Tc > 249ms.
For instance, I have:

CIR = 64,000
Be = 8000
Tc = 125ms in "show traffic-shape"

Exactly as we would expect. However...

CIR = 64000
Be = 16000
Tc STILL = 125ms in "show traffic-shape"

But wait, theres more : )

CIR = 64000
Be = 15999
*Tc = 249ms*

hmmmmm....relevant show output below. Is there a 249ms limit?

R2(config-fr-dlci)#do sh ver | i 12.4
Cisco IOS Software, 3600 Software (C3640-IK9O3S-M), Version *12.4(23)*,
RELEASE SOFTWARE (fc1)

R2(config-map-class)#do sh run | s map-class
map-class frame-relay FRTS
 frame-relay cir 64000
 frame-relay bc 8000

R2(config-map-class)#do sh run int s2/0
Building configuration...

Current configuration : 474 bytes
!
interface Serial2/0
 no ip address
 encapsulation frame-relay
 ipv6 address 2001:0:0:200::2/64
 ipv6 address FE80::2 link-local
 serial restart-delay 0
 no fair-queue
 frame-relay traffic-shaping
 frame-relay map ipv6 2001:0:0:200::2 206
 frame-relay map ipv6 2001:0:0:200::4 204 broadcast
 frame-relay map ipv6 2001:0:0:200::5 205 broadcast
 frame-relay map ipv6 2001:0:0:200::6 206 broadcast
 *frame-relay interface-dlci 204
  class FRTS*
 no frame-relay inverse-arp
end

R2(config-map-class)#do sh traffic

Interface Se2/0
       Access Target Byte Sustain Excess Interval Increment Adapt
VC List Rate Limit bits/int bits/int (ms) (bytes)
Active
204 64000 1000 8000 0 *125* 1000 -

R2(config)#map-class frame-relay FRTS
R2(config-map-class)#frame-relay bc *15999*

R2(config-map-class)#do sh traffic

Interface Se2/0
       Access Target Byte Sustain Excess Interval Increment Adapt
VC List Rate Limit bits/int bits/int (ms) (bytes)
Active
204 64000 1999 15999 0 *249* 1992 -

R2(config)#map-class frame-relay FRTS
R2(config-map-class)#frame-relay bc *16000*

R2(config-map-class)#do sh traffic

Interface Se2/0
       Access Target Byte Sustain Excess Interval Increment Adapt
VC List Rate Limit bits/int bits/int (ms) (bytes)
Active
204 64000 1000 16000 0 *125* 1000 -

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Joe Astorino - CCIE #24347 R&S
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