ExchangeVersion

Hi

We are running Exchange Server 2013 and we have completed migration from Exchange Server 2007
However, the ExchangeVersion does not display v15 for all components

Get-ExchangeServer        ExchangeVersion        0.1 (8.0.535.0)
Get-DistributionGroup        ExchangeVersion        0.10 (14.0.100.0)
Get-DynamicDistributionGroup    ExchangeVersion        0.10 (14.0.100.0)
Get-Mailbox            ExchangeVersion        0.20 (15.0.0.0)
Get-MailContact            ExchangeVersion        0.20 (15.0.0.0)

Before I ignore I want to ensure that this is normal, are there any article on this attribute?

shapi