This article describes a simple way to estimate the size (in bytes) required for the PasswordData blob.
The PasswordData blob can contain up to 32 history passwords.
It also contains:
Each of them is taking up to 1024 bytes.
Therefore you should multiple the number of passwords to keep in the history by 1024, then add a buffer of a few more kilobytes.
So it makes 32.768 bytes + buffer. The PasswordData blob should have a max size of 40kB.