On day one Conner collects 32 rocks because 8 x 4 = <<8*4=32>>32
On day three Sydney collects 64 because 32 x 2 = <<32*2=64>>64
After three days Sydney has 915 rocks because 837 + 0 + 4 + 64 =<<837+0+4+64=905>>905
Before the third day Conner has 878 because 723 + 32 + 123 = <<723+32+123=878>>878
Conner needs to collect 37 on day three to tie Sydney because 905 - 878 = 27
#### 27