GCSE Chemistry Question Help

Hi, im stuck on question 2(a) and i dont know how they got the conclusion that "both B and C have a dot at 9 cm" and "it is the highest dot (in C) ",
pastpaper - https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FChemistry%2FGCSE%2FPast-Papers%2FWJEC-Wales%2FUnit-1H%2FJune%25202022%2520QP%2520-%2520Unit%25201%2520(H)%2520WJEC%2520Chemistry%2520GCSE.pdf

Mark scheme - https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FChemistry%2FGCSE%2FPast-Papers%2FWJEC-Wales%2FUnit-1H%2FJune%25202022%2520MS%2520-%2520Unit%25201%2520(F%2520and%2520H)%2520WJEC%2520Chemistry%2520GCSE.pdf

Reply 1

nerfgun2

total distance to the solvent front from pencil line is 15cm, then u times 0.6 by 15 to get the distance travelled which is 9cm. then read across from 9cm which gives u B and C. however in B it is the second highest dot, whereas in C its the highest dot and the question is asking for the highest Rf value, meaning the highest dot therefore making ur answer C. hope this helps