In conjunction with the unveiling of interactive textbooks in iBooks 2 for the iPad (see “Apple Goes Back to School with iBooks 2, iBooks Author, and iTunes U,” 19 January 2012), Apple has released iTunes 10.5.3, whose only change is support for syncing these new titles between iTunes and an iPad running iBooks 2. (Free, 102 MB new download or 10.5 MB via Software Update)
It appears that 10.5.3 fixed the erroneous storage space bar depicted in 10.5.2. Previously iTunes would show my iPhone and iPsd were over the storage limit when there was room to spare. now it is accurate.
Don't know where the 10.5 MB update is, but it isn't in Software Update.
Software Update is saying the size is 79.1 MB. I'm going from iTunes 10.5.2 (11).
Curious. Are you perhaps on a PowerPC-based Mac? It was 10.5 MB in my Mac Pro in Software Update. We probably shouldn't bother to publish how large things are in Software Update, since those numbers can vary by installation, but in this case it was so much different than the full download that I went with it.