Until recently in all forms of IT the kilobytes always meant multipliers/divisors of 1024 - this is because whilst 1000 is a round number in decimal, 1024 is the nearest round number in binary (when changed back to decimal) Computers, unlike humans, count in binary
Recently some systems have started to use 1000 as the multiplier for kilobytes (just to make things easier for humans), however Backup Exec should still be using 1024
You should probably be asking a more generic question (outside of Symantec) as there are probably less software tools that divide by 1000 when enumerating the bytes in memory or storage, so you would be better off trying to identify what software tools these are and assume that unless you know different that they all divide by 1024.
EDIT: If you read http://en.wikipedia.org/wiki/Kilobyte you will see that the term KB/kilobyte has historically been used for both 1000 and 1024 multipliers and yes the IEC did internationally redefine the definitions, but that does not mean that software houses followed the change in standards,
EDIT2: As the operating system itself uses 1024 multipliers for disk storage whilst still using KB, MB etc, it may be a while before software houses change to the new definitions.
To see what I mean use windows explorer to find a file that is more than a 1MB in size - I chose one that was 4MB.
In Windows Explorer the Column view lists the file size in KB (mine was reported as 4,297 KB). Then right click the file and bring up the preoperties. This will show the MB size followed by the byte size in brackets) mine reports as 4.19MB and 4,399,837 bytes . If you do the maths on these figures you will see that Microsoft is using 1024 multipliers
