Buy and Hold strategy in rebalancing Question investment, confusion, following

yospaghetti

sorry if this has been asked before.
My confusion is on schweser notes book 5, page 50
the slope 0.6 indicates that 60% of total assets are originally invested in stock.
assuming initial investment of 10 dollars, 4 dollars in bills and 6 dollars in stock. stock price increases from 6 to 8 dollars. shouldn’t the total assets increase from 10 dollars to 12 dollars? I am not quite following what the slope 0.6 in that graph mean. Please help, thanks!