Why are you thinking you need to attend mediation? Mediation applies to parenting matters, not property. I suspect you will benefit from getting some early advice.
You can go for mediation, but you should understand how the process works before starting it and what rights you have.
If the ex's lawyer has a set % in mind, and the ex is insisting on following her lawyer's advice, then mediation is a waste of time and money. Much depends on whether your ex is a reasonable person as mediation only works when 1) one person concedes because they can't handle the stress or 2) both parties are reasonable and willing to give a little.
I can also arrange for legal advice if you want to speak with a lawyer
My email address is on
www.vichelp.com.au