I could be wrong, as I haven't done any audit or testing on this feature yet, but there's a user setting "Cooling shrinkage" in your equipment profile for this.

https://www.brewersfriend.com/homebrew/profile/equipment
As far as I understand it, the recipe editor calculates all volumes (including preboil, postboil, and boil off rate) at room temperature, and the brew session log allows for temperature corrections to a degree. The formula used is linear, according to the documentation.

For those that like math...

Engineering toolbox has a chart of volumetric temperature expansion of water, which is what I based my formula on. Note that there's likely a weak relationship with gravity that is currently ignored as there's no data to know how it works. Engineering toolbox's data has a coefficient of 1.043841 at standard temperature and pressure, and shows a R^2 value of ~94.7 for linear functions, but 99.93% for a 2nd degree polynomial with greater accuracy as more terms are added.

Click to expand...