In case only a non terminal functional group or a substituent group is present in the parent chain, the numbering should start in such a way that the substituent or the non terminal func. group gets the lowest possible number. Is this statement completely correct?

When a non-terminal functional group or a substituent group is present in the parent chain, the numbering should start in such a way that the non-terminal functional group (for example, ketone) should get the lowest possible  number followed by the substituent.

For example, 3-methyl-2-butanone. In this compound the numbering will start in such a way that, fuctional group shouls get the nlowest possible number which is 2 in this case followed by the substituent group which is methyl will get the next lowest possible number.