It looks to me like a miss-typing

it must be 200g of Water at 20C + 60g of ice at -40C

I don't understand your notation:

are you using the "." as a multiplication symbol?

are you using the "." as a decimal place?

are you using it as both?

or something different?

As a programmer, I find the use of "*" quite natural for a multiplication symbol,

but this is personal preference.

It matters little

__as long as it is clear__ what convention is being employed.

The inclusion of brackets can (hugely) improve the readability of equations.