Question

when using significant figures, why is 2.8023 - 4.762 = -1.960 instead of -1.961

Answer 1

we have 4 significant figures in this problem because
4.762 (four numbers) is not 4.7620 (five )
so the problem is really
2.802 - 4.762 = -1.960

Answer 2

so does this apply to everything else where you round all the numbers down to the number with the least significant figures?

Answer 3

yes, if you only know one of them to 3 decimal places, there is no point in carrying more in the others.