Hi O250,
I'm not sure if this addresses your question, but the tutor we used for several months prior to the entrance exam said that, based on her experience of previous pupils, a score of 70+% is a good indicator of passing. This seemed a little low to me.
If you think of a non-standardised test (and I know these aren't that and this is a very rough rule of thumb, but) with one point allocated to each of the 423 questions, a score of 334 would equate to 78.96%. For AGGS I would aim higher.
As others have said, at this stage you would do well to focus on any problem areas so that your daughter gains in confidence; a mock to help evaluate the situation [edit: by a 'reputable tutor'*] would help with that. Practice with timing and 'strategy' would come next, but I wouldn't worry about timing until the months before the exam - your daughter's score will increase plenty between now and then.
Rest and fun and important too

for you and for her.
*simply because they will provide a detailed report breaking down your child's performance in key subject areas.