There are 50 lines in voltage scale from zero and it has three basic scale (10, 50, 250). To know the volts per lines, you need to divide the scale/range to 50.
10 ÷ 50 = 0.2 (in 10 scale each line is 0.2V)
50 ÷ 50 = 1 (in 50 scale each line is 1V)
250 ÷ 50 = 5 (in 250 scale each line is 5V)
1000 ÷ 50 = 20 (in 1000 scale each line is 20V)
2.5 ÷ 50 = 5 (in 2.5 scale each line is 0.05V)