Problem calculating extra hours (Work Shift)

[Googles]

Hello,
I am trying to count the number of the additional hours for my Employee in my Shift calendar:
For example in February: an Employee has 5 additional hours in the month. But he has minus hours in January
Note: that the calculation method is the day, and 1 day = 8 hours
I have used the Mod() and the INT() function in the example shown below, is this true or wrong?

	A	B	C	D	E	F	G	H	I	J	K	L	M
1	12/2019	1	2	3	4	5	6	7	8	9	10	11	12
2		20	21	19	20	12	19	21	21	20	18	17	10	Work days per Month
3		19	21	19	20	12	21	21	21	19	18	17	10	Empleey day Worked
4		-1	0	0	0	0	2	0	0	-1	0	0	0	Days Minus plus
5		-8	0	0	0	0	16	0	0	-8	0	0	0	Hours Minus plus
6		0	0	0	0	0	0	0	0	0	0	0	0
7		-8	-8	0	0	0	16	16	0	-8	-8	0	0	Hours Minus plus

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B4: =B3-B2
B5: =INT(B4*8)+A6
B6: =IF((A5+B5)<0,MOD((A5+B5)/8,-1)*8,MOD((A5+B5)/8,1)*8)
B7: =INT(B4*8)+A5

- In the event that the employee has incomplete working hours, you must move to the next month.
- In the event that the employee has additional hours, the missing hours shall be completed first and the remainder shall be counted as an additional.

Sorry about my English
I hope the you understand me !

thanks