Get Size info for each users Managed custom folder.

$Mailboxes= Get-Mailbox -Database "mailbox database 1" 

foreach ($mailbox in $Mailboxes)
{
    $MBStats = Get-MailboxFolderStatistics $($mailbox.SamAccountName) -FolderScope ManagedCustomFolder -IncludeAnalysis | where {$_.Name -eq "Company Records"} | select Name, FolderAndSubfolderSize
    #Write-Host $mailbox.name + ", " $mailbox.SamAccountName  + ", " $MBStats.Name + ", " $MBStats.FolderAndSubfolderSize
    $mailbox | Add-Member -MemberType NoteProperty -Name ManagedCustomFolderName -Value $($MBStats.Name)
    $mailbox | Add-Member -MemberType NoteProperty -Name ManagedCustomFolderSize -Value $($MBStats.FolderAndSubfolderSize)
}

$Mailboxes | select name, samaccountname, ManagedCustomFolderName, ManagedCustomFolderSize