Eurocode 8 lateral forces issue

[Mazi24]

Dear Users,

Does anybody have any idea why in ETABS and SAP2000 seismic loadings for EUROCODE8 are calculated based on weight and not mass.

The formula in code is (Fb = Sd * m * Lambda) but in lateral force manual which comes with these softwares it is stated as (Fb = Sd * W * Lambda) and by checking the outputs all results are greater than what I expect:

By using mass (which I think is correct):
Fb = Sd(m/s2) * m(kg) * Lambda(unitless) = kg.m/s2 = N

However by using weight (ETABS and SAP2000):
Fb = Sd(m/s2) * W(N) * Lambda(unitless) = N.m/s2 which is not force anymore

Thanks in advance.
Regards,