A great many Indian sweets are the same few ingredients taken to different points on one continuum. That continuum is sugar syrup, and the stage it reaches is the recipe's real instruction.
Concentration changes everything about sugar
As a syrup boils, water leaves and the proportion of sugar rises. Each successive stage produces a syrup with different viscosity, stickiness and setting behavior.
A thin syrup soaks into a fried dumpling and stays liquid. A thicker one clings and sets into a chewy coating. Thicker still and it crystallizes as it cools.
These are not different ingredients or techniques. They are one process stopped at different moments, which is why syrup stage is the variable recipes obsess over.
Traditional tests describe behavior, not numbers
Cooks judge stages by pulling a cooled drop between finger and thumb and counting the threads it forms, or by dropping syrup into cold water and observing whether it holds shape.
These tests work because they measure the property that matters, which is how the syrup behaves at eating temperature rather than how hot the pan is.
A candy thermometer, common in American kitchens, gives the same information more repeatably and is worth using while learning what each stage looks like.
Why sweets fail at the last minute
Syrup passes through stages quickly near the end, because there is progressively less water left to remove. A minute of inattention moves it a full stage.
Overshooting is not recoverable by adding water, since that resets the syrup and it must be reduced again, changing color and flavor along the way.
Undershooting shows up later as a sweet that never sets or a coating that stays tacky, which is why cooks test rather than time.
What an American kitchen brings to this
Plain granulated sugar is exactly right, and the fine crystals sold in US supermarkets dissolve readily without needing to be dissolved separately.
A heavy-bottomed saucepan matters more than the sugar, since thin pans scorch syrup at the edges and darken the whole batch.
Electric ranges lag when turned down, so pulling the pan off the element at the target stage is more reliable than adjusting the dial.
Crystallization is the failure to control
Stray sugar crystals on the side of the pan can seed the whole syrup and turn a smooth batch grainy in seconds.
Washing the pan sides down with a wet brush, and adding a small acid such as lemon juice, both interfere with crystal formation.
Where graininess is the goal, as in fudge-like sweets, cooks encourage it deliberately by stirring during cooling. The same physics, used on purpose.