Why BkVFLss is larger than GlobGnd in bifacial system simulation results?

[Siping]

This is what GlobGnd and GkVFLss described in PVsyst help

GlobGnd	Global incident on ground, below the system.
ReflLss	Ground reflection loss (albedo)
BkVFLss	Loss due to the view Factor for rear side

So I think GlobGnd is source energy for other parameters such as ReflLss and DiffGnd etc. That means value of GlobGnd should be the largest during these parameters.

But I processd some simulation  and looked into details of results. I found that BkVFLss always larger than GlobGnd. Does anyone know why about this?

	GlobGnd	DiffGnd	ReflLss	BkVFLss
	kWh/m²	kWh/m²	kWh/m²	kWh/m²
January	26.1	9.94	13.06	18.8
February	41.5	13.76	20.73	35.4
March	70.9	23.17	35.45	67.1
April	98.7	27.04	49.34	96
May	125	28.2	62.51	121.1
June	124	29.7	62	119
July	122.1	32.43	61.07	117.3
August	103.1	31.35	51.56	99.9
September	75.3	24.16	37.64	72.3
October	52.8	18.7	26.41	47.2
November	30.3	12.88	15.13	23.6
December	20	10.03	10	14.4
Year	889.8	261.35	444.88	832.2

albedo=0.5   GlobGnd=889.8   BkVFLss=832.2

	GlobGnd	DiffGnd	ReflLss	BkVFLss
	kWh/m²	kWh/m²	kWh/m²	kWh/m²
January	26.1	9.94	5.22	30
February	41.5	13.76	8.29	56.7
March	70.9	23.17	14.18	107.4
April	98.7	27.04	19.74	153.6
May	125	28.2	25	193.8
June	124	29.7	24.8	190.4
July	122.1	32.43	24.43	187.7
August	103.1	31.35	20.62	159.9
September	75.3	24.16	15.06	115.7
October	52.8	18.7	10.56	75.5
November	30.3	12.88	6.05	37.7
December	20	10.03	4	23
Year	889.8	261.35	177.95	1331.5

albedo=0.8  BkVFLss=1331.5

[Michele Oliosi]

Hi,

The reason is that GlobGnd, DiffGnd and ReflLss are variables that refer to the m^2 of ground area.

Whereas, BkVFLss refers to the m^2 of PV modules.

If you were to mutiply by the respective surfaces (ground surface > module surface), the energy hierarchy would make sense.