'Better spare at brim than at bottom' meaning

[Ali1002]

Hi!
What does 'Better spare at brim than at bottom' mean?
I see this proverb somewhere in the dictionary.
For example, to define the word 'Spare' or 'brim'.
While I know the meaning of those words, I'm not able to understand the meaning of the whole sentence.
I think it means that 'it is better to have the extra things of the brim rather than the bottom', but I'm not sure at all!
Would you help me to understand what it means, please?
Sorry for my bad.

 

[Tdol]

I had not heard it, but according to an old book of proverbs, it means that it is better to be sparing when you are young (a full cup) than to have to be frugal when you are old.