Conditional evaluation

[Gribouillis]

It seems that you inverted the condition implied by your first post! You could also try something like

>>> a1, b1 = 140.2, 6543.5
>>> silos1a = b1 - a1 - bool(b1 > a1) * 6553.5
>>> print(f'Расход: {silos1a:.1f}')
Расход: -150.2

This amounts to using bool() as a programmatic version of the Iverson bracket used by mathematicians.