600TC 100% Cotton 4pc Sheet Set-Solid

Are these 600 single ply? Or more like 150 thread (but counting each ply as a separate thread?)

here is the information on the sheets. These sheets are excellent sheets.

100% cotton
Single-ply yarn
Thread count: 600
Durable cotton sheets can last for years, growing softer as they wear
Highly breathable, cotton sheets feel cool and comfortable in warm weather and are ideal for layering all year
Care Instructions
Machine washable
Tumble dry low
Fit Information
Pocket depth: 15”
Stretchable jersey/lycra pocket conforms to most mattress sizes
Maintains a tight, secure fit that won’t shift throughout the night

Thinking about buying these has anyone tried this exact set of sheets out yet? Bit leery of buying sheets online