Why is it important to mark the solvent level on the chromatography paper as soon as you remove it from the Petri dish?

The importance of marking the solvent level on the chromatography is -

Since,

the solvents are volatile in nature and if they are not marked immediately, the solvent can get evaporated, and the exact level of the solvent would be lost, and hence,

it will give an inaccurate data of the experiment.