I think it represents CSS Grid line numbers

• Positive numbers start from left/top, so it starts at 1 and increases from left-to-right and top-to-bottom.
• And Negative numbers is from right/bottom, it starts at -1 and decreases.

So in your layout,

• Student status shows (1) indicating it starts at the first grid column line
• Date selection shows (2) indicating it starts at the second grid column line
• Text div showing (1) to (-1) means it spans from the first grid line to the last grid line
• Radio buttons showing (3) to (-1) means they start from the third grid line and extend to the end

Thanks