Last Trade refers to the price at which the last shares moved across the board (changed ownership).  It stays that way until the next trade.  In your scenario of BID $8.10 and $ASK 8.35, LAST $8.25 the last to trade did so at $8.25 while the next buyer in line is offerring to buy at $8.10 but the next seller in line is offerring to sell at $8.35.   Normally the spread between Bid and Ask would be much less but on a light trading day when volume is low such spread can occur. 

Occasionally you will also have somone slip an 'all or nothing' Bid or Ask in between the spread and someone will snap it up but then the previous spread reappears.

Hope this helps.