[MC-139665] "Preparing spawn area" can sometimes display negative numbers and percentages over 100

When creating a new world, the world progress screen sometimes displays negative work or percentages greater than 100.

Not sure if this is related, but this issue was discovered while testing MC-139648. This happened while creating a snowy tundra buffet world.

Linked issues

I have also seen values over 100% This was using local game with default settings except for cheats turned on.

Confirmed this 3 times in 2 different buffet worlds (Snowy Taiga & Ocean).

It does not affect normal and superflat worlds for me.