Ascending order and invoice numbers - J. 3.4 - VM 3.0.6

[Three_d]

Hello,

Why aren't the order and invoice numbers in Joomla 3.4 - VirtueMart 3.0.6 ascending?

[Milbo]

They are ascending.

[Three_d]

You're right but why are the characters at the beginning of the ordernumber and at the middle of the invoice number random.
And can I get rid of those characters.

I've for example the following ordernumbers and invoice numbers:
I don't understand the bold characters?

Order numbers
271603
93f104
bc8505
ade606

Invoice numbers
15022773805
1503010db06
150302c1d07
150309a2e08

[Milbo]

Kind of self encrypted. It prevents that someone can guess an order number. http://extensions.virtuemart.net/vm-orders/order-number-plugin-detail

[Three_d]

Thanks Milbo!