You can also do the following to get the data for Announcement space on the gateways try a "list integrated-annc-boards " instead of display and you will get a list of announcements with time remaining etc , but this will also show you any that are 0 in size that can be binned off , the missing information between Kevin`s output and yours is probably down to Firmware , as my 6.3 system gives different out put again , and some fields on that display is only for TN circuit packs.
If you issue the command on the gateway "show announcement files" you will be given at the very bottom a read out of the compact flash memory used and spare by announcements , "show system" will tell you what you have in RAM and in compact Flash , so if you get the capacity for your used space in the TN2501 val pack , you will be able to work out.
Also read this , but as a min G450 provide 45min announcement and the TN2501 60 min , so even with one gateway you are not far off and that can be upgraded to 240 min
ACSS (UC/SBCE/SM/SME)
Not that they mean a thing anymore , get a brain dump pass the test crash the system.