What is data[10+:4] data[10-:4]

You give the anwser to your question ;)

The first number is the bit to start from, then the +/- gives the direction, and the second number gives the number of bits.

Therefore [10+:4] means [10:13] and [10-:4] means [10:7]

I didn't know this kind of construction in Verilog, and I wonder if it wouldn't add confusion to a code if you start mixing it with the traditionnal vector representation...