Varsh Kundlee is prepared based on the crossing of  Sun transit (Gochar Sun) on natal Sun in lagan chart (Birth chart/Janam kundlee). In other words to be more exact, the year begins when the transit Sun reaches the exact longitude of the natal Sun.

Varsh Kundlee depict the rashi, house and positioning of all the planets in the chart based on Varsh kundlee and is different with respect to Lagan chart. 

Varsh Kundlee is analyzed and interpreted the predictions, which are made based on this chart for one year only. So the period of interpretation can be reduced to one year and gives results for narrow period of time.