I've looked all over for information but I just don't understand how the state by state votes are tallied during the convention. After watching the DNC broadcast tonight I was confused to see that Biden, despite losing California and Nevada's primaries to Sanders, had more votes cast for him in each state during the "roll-call."

I understand that there were previously unpledged superdelegates which have since been all but abolished before this primary, so how does Biden come away with more votes in two states which he lost? The California votes tally up to 494 so that makes sense, but Biden ended up with nearly 100 more votes than he got in the primary which he lost.

I assume that some votes were "given up" from the Warren campaign or whatever, and that Biden also received the remaining 79 or so unpledged delegates, but then I thought that these delegates were no longer able to vote for whoever they wanted. Anyway any information on how this works would be great. Thanks!