the last two columns are the daily returns...so you were saying something about rebasing but if you think about it looking at the daily percentage return is the same thing as rebasing(i suppose)...either way, the scatter graph is looking at the relationship between the returns of BLAND/LAND and the daily return is the thing you want to compare.
so if you look at the r-squared it is 0.8 (or whatever) which means that x explains 80% of the moves in y (r-squared isn't the same as correlation although someone else should explain the difference tbh as my grasp is weak at best). i can't remember exactly how you do the ratios, i've never done pair trading seriously, there is an ig index pdf somewhere that explains everything in detail though. (i would hazard a guess that you just do the same monetary amount, as the volatility is controlled by looking at daily percentage returns, although im probablly wrong).