What it means
Each of the seven planets awards a bindu, a point, to certain signs counted from every other planet and from the ascendant. Collect what one planet receives and you have its Bhinnashtakavarga row; add all seven and you have the Sarvashtakavarga, which is what people usually mean by 'my Ashtakavarga'.
How it is read
The totals are fixed by the tables, not by the chart: every correct row sums to its published figure (Jupiter 56, Mercury 54, Saturn 39) and the twelve signs always total 337. That makes 28 the average per sign, and the number to read each sign against — a peak somewhere requires a trough elsewhere.
What to watch for
It is a transit-timing tool, not a verdict. The usual practice is to check the sign a planet is transiting against that planet's own row: four or more of its own bindus reads as a productive passage. The 30/25 thresholds in common use are practitioner conventions, not figures from Bṛhat Parāśara Horā Śāstra, which gives the tables and not the cut-offs.