621 is the VCP exam for 6.0, and 602 is the Foundations exam for 6.5 - that combination would give you VCP6-DCV NOT VCP6.5-DCV.
To get VCP6.5-DCV you would have to pass the VCP exam for 6.5 - the 622.
You'd also need to meet the training requirement for either VCP6-DCV or VCP6.5-DCV - check Path 1 on either page.