Regarding error: Incompatible version of the serializing p..

I received the error, "Incompatible version of the serializing package.
(0x80070724)", while trying to perform a windows backup. I used the KB
article, "http://support.microsoft.com/kb/940970/en-us". However, on step 4,
I forgot to note down the Maximum Shadow Copy Storage Space value.

At step 8c, it asked me to put that number back in but I did not write it
down so I left it as 300MB as step 5.

Should I leave it at 300MB or is there a way to get the original value back?
What are the implications of setting it as 300MB?