Repitching from slurry question

[Mther]

Good afternoon,

I have 125ml of very thick yeast in a 500ml bottle. I harvested this on 10/6/14. I used Mr Malty calculator for OG 1.062, 15L Volume, 4.5 billion/ml yeast concentration, and 10% non-yeast percentage.

I need 170 billions yeast cells and 420ml of yeast according to Mr Malty. Does that mean that the 125ml have 50.6 billion cells?

Instead of using 420ml of thick yeast, can I (according to brewersfriend calc) make a ~3L yeast starter (shaking) to achieve the target? I have more harvested yeast but I think a yeast starter would be more reliable rather than using 420ml of a 5 months old harvest?

Please let me know if I am doing something wrong.

Thank you in advance.