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Do marketmakers always quote a bid and ask simultaneously
Market makers (shortened MM) in an exchange are generally required to list both a bid and ask price to allow both buyers and sellers to trade and keep the market moving.  However, a more general idea of a MM may includes companies off an exchange (say large banks acting as broker/dealers in an over-the-counter market) are not required to give a simultaneous bid/ask, but often will on request.  So, it might depend on where you are getting this data but likely the bid/ask was quoted simultaneously. An exchange, like the NASDAQ for instance, may have multiple MMs for a given market.  The "market" spread will be from the highest bid to the lowest ask over all the MMs.  The highest bid and lowest ask may come from different MMs and any particular MM often will have a larger spread. The size of the spread gives a rough idea of how much a MM is trying to make off of a "round trip" trade (buying than immediately selling to someone else or selling than immediately buying from someone else).  Of course, immediate round-trip trades are not always possible and there are many other complications.  However, half the spread is a rough indicator of how much they hope to make off of a single trade.