OK Sculp, I'll bite....
"K" means the trade set the last price of the day, in this case, $2.55
"W" means the hidden or iceberg portion of the order was not filled.
In the last 10 trades, RBC was the seller of 23,600 shares.
RBC probably has an iceberg at $2.55, in other words, a big block at $2.55.
How'd I do, professor Sculp?