I don't know but 0615 sounds late to open (and later than the advertised booking office opening time).
Other TOC websites say 0515 for these car parks.
Maybe message Avanti on Facebook if you're on it, as they're usually quite fast at replying.
For Warrington, I tend to prefer to park at Time Square Multistory, which is 24/hr with money going to the council rather than CCP. It's not all that much further than Slutchers Lane either.
Warrington Bank Quay car parks are 24/7, barrier operation to enter/exit.
Take a ticket a barrier, and pay on exit.
At first I was thinking it was ticket office opening hours or station opening times displayed by mistake. But even they don't match.Useful to know about that option, thanks!
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Must be outdated information on their website...they replied to me on messenger linking to part of their website which says 0515, looks like probably just one page is wrong which happened to be the one I looked at!