On recyclable products inside the recyclable symbol what do the numbers inside that mark stand for?

Its for the type of plastic the item is made of. Its called SPI resin identification coding system.

1-PETE or PET Polyethylene Terephthalate Recycled to produce polyester fibres, thermoformed sheet, strapping, soft drink bottles.

2- HDPE High-Density Polyethylene Recycled to become various bottles, grocery bags, recycling bins, agricultural pipe, base cups, car stops, playground equipment, and plastic lumber.

3-PVC or V Polyvinyl Chloride Recycled to become pipe, fencing, and non-food bottles.

4-LDPE Low-Density Polyethylene Recycled to become plastic bags, various containers, dispensing bottles, wash bottles, tubing, and various molded laboratory equipment.

5-PP Polypropylene Recycled into auto parts and industrial fibers.

6-PS Polystyrene Recycled into a wide range of products including office accessories, cafeteria trays, toys, video cassettes and cases, insulation board and expanded polystyrene products (e.g. Styrofoam).

7-OTHER Other plastics, including acrylic, polycarbonate, polylactic acid , nylon and fiberglass.