Need to set account balance buffer in Instant Transfer settings

[365NDaardvark]

I want to set a buffer on my instant transfer configuration but it only gives me option to transfer entire balance.  On my other paypal account, it gives the option to keep a buffer on the account which I use to enable me to process customer refunds even after a transfer has taken place (which would normally deplete the balance).  How do I get this option to show on an account that isn't currently showing it?

I want to see this:

Buffer option on my other account

But all I see is this: