What determines the size of the grid in each section?

Can anyone tell me what determines the size of the grids in each section?  And, I'm not talking about the padding which can obviously be adjusted many ways. I'm talking about the physical size/dimension of each set of blocks in a section's grid. Why are some grids so small while other are so much larger? Is it the content added to the section? If so, why can one text block have  small grid boxes while another text has much larger grid blocks. For instance, when two sections are side by side (horizontally) it's nearly impossible to align the 2 text headings vertically because the grids are different sizes. See attached.   

Bueller.... Bueller....anyone, anyone?  Is anybody home in here? 

I am looking for an answer to this question too.