Chara Dasha is the flagship rasi dasha of the Jaimini system: it progresses through signs rather than through planets, and the length of each sign's period is the count from that sign to the house its lord occupies. That single rule is why Chara periods are unequal, running from one year to twelve, unlike the fixed years of Vimshottari.
BPHS 46.155 to 46.156 states the rule: the number of years of a dasha is reckoned from the rasi up to the house in which its lord is posited. So if the lord of the dasha sign sits five signs away, that sign gets five years. A lord in its own sign gives the full twelve, because the count runs the whole way round.
The direction of that count is the part most implementations get wrong. It is decided by the footedness of the sign, its pada, not by modality and not by odd-or-even parity. The odd-footed signs are Aries, Taurus, Gemini, Libra, Scorpio and Sagittarius; the counting runs one way for those and the other way for the rest, and AstroZivi derives it from the shared Jaimini rule so that Chara and the other rasi dashas cannot drift apart.
Vimshottari is a nakshatra dasha: it is anchored to the Moon's birth star, its lords are planets, and its periods have fixed lengths adding to 120 years. Chara is a rasi dasha: it is anchored to the ascendant, its lords are signs, and its lengths are computed per chart, so no two charts share the same sequence of period lengths.
Because of that, the two are read with different apparatus. Chara is interpreted with the Jaimini karakas and the arudha padas rather than with the planetary significators of the Parashari stream. Running both on one chart is normal practice; treating a Chara period as though it were a Vimshottari mahadasha is not.
It builds the full Chara sequence from your birth chart, with the sign, its lord, the period length in years and exact start and end dates, and nests the antardashas inside each mahadasha. Everything follows from the count-to-lord rule above and from the rising sign, so an accurate birth time is required: change the ascendant and you change the entire sequence.
The page reports structure and dates. It does not attach a prediction to a sign's period, because a Jaimini reading needs the karakas, the arudhas and the argala of the chart, which is a full analysis rather than a calculator output. What is exact here is the timing skeleton.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.