They're indications of the purpose of each light. In all honesty, you'd have to ask the designer.
But, to take a stab at each:
"Fill <\" would be a
fill light (ie, not the key or principal light) from
stage left; but possibly
stage right. I've known different designers who use that arrow designation both ways (from
stage left or from
stage right.) The slash indicates that the angle of light isn't a true side or high side, but more from in front at an angle.
"Ft Ml" might possible be front light for mid-stage left.
"X/Lt < D" would be "cross-light" from the same direction as the
fill light above. "D" could mean a number of different things.
"Wm </" would be a warm, from the same side as before, opposite angle as the fill.
"Moat < DL" would refer to a set area, possibly specific to the
play; but I've also heard "moat" refer to the area
downstage of a raised
platform, usually in a full lane from
stage left to
stage right. "In 1," as it were. So, sidelight for the moat, specifically hitting the
downstage left portion.
But really, your best bet is to ask the designer. You can use it as a good prompt to ask other questions about the design intent for the show, hopefully bridge any other uncertainties in language or terminology, and
gain some insight into the designer's process.