[Spambayes] What does Delayed cost mean?

[Zhang Le]

Hi all you spambayes folks,
  I've downloaded spambayes and played with it for a couple of days.
  It's fun to learn a good language through such a researh project.
  I can test some new ideas within current spambayes framework, really
  fun!
  When running one test I got the following msg:

...
-> best cost for all runs: $9.00
-> per-fp cost $10.00; per-fn cost $1.00; per-unsure cost $0.20
-> achieved at 26 cutoff pairs
-> smallest ham & spam cutoffs 0.22 & 0.975
->     fp 0; fn 2; unsure ham 9; unsure spam 26
->     fp rate 0%; fn rate 0.417%; unsure rate 1.87%
-> largest ham & spam cutoffs 0.28 & 0.98
->     fp 0; fn 2; unsure ham 9; unsure spam 26
->     fp rate 0%; fn rate 0.417%; unsure rate 1.87%
-> <stat> all runs false positives: 8
-> <stat> all runs false negatives: 6
-> <stat> all runs unsure: 0
-> <stat> all runs false positive %: 0.575539568345
-> <stat> all runs false negative %: 1.25
-> <stat> all runs unsure %: 0.0
-> <stat> all runs cost: $86.00
Total messages: 1870; 1390 (74.3%) ham + 480 (25.7%) spam
Ham: 1382 (99.42%) ok, 0 (0.00%) unsure, 8 (0.58%) fp
Spam: 474 (98.75%) ok, 0 (0.00%) unsure, 6 (1.25%) fn
Score False: 0.75% Unsure 0.00%
Standard Cost: $86.0000
Flex Cost: $86.0000
Flex**2 Cost: $86.0000
Delayed-Total messages: 1870; 1390 (74.3%) ham + 480 (25.7%) spam
Delayed-Ham: 1381 (99.35%) ok, 9 (0.65%) unsure, 0 (0.00%) fp
Delayed-Spam: 452 (94.17%) ok, 26 (5.42%) unsure, 2 (0.42%) fn
Delayed-Score False: 0.11% Unsure 1.87%
Delayed-Standard Cost: $9.0000
Delayed-Flex Cost: $75.5407
Delayed-Flex**2 Cost: $61.8529

My question is :what does Delayed cost mean?
Where is *delay* come from? Since I just use one training set and one test
set.

Thanks in advance.
--
                                     Sincerely yours,
                                            Zhang Le