Rows = prices around the current LTP (±8 ticks, higher price = drift at the top). Strong bar = £ matched at that price in the chosen window; faint bar behind = total matched at that price so far (whole market, from the capture's tv_* columns). The two bars use separate scales.
■ backers taking (price at or above the previous best lay) · ■ layers taking (at or below the previous best back) · ■ between the two. Side is estimated, same rule as the backers/layers lines.
Yellow box = LTP · B / L = best back / best lay now. A price only counts once it has been seen in the top 3 or at the LTP, so money matched while a price was out of view shows when it comes back into view. Past data only.