Understanding Society User Support

Hi,

I am trying to merge individual files across waves 10 and 11 into wide format to create a 2019 calendar year dataset.
I used this method from "Box 1: Example syntax for pooled analysis for cross-sectional estimation relating
to calendar year 2011, with weight re-scaling" in https://www.understandingsociety.ac.uk/sites/default/files/downloads/documentation/user-guides/mainstage/weighting_faqs.pdf

ge wts=0
replace wts=indpxui_xw if month>=13 & month<=24
ge ind=1
sum ind [aw=indpxui_xw] if month>=1 & month<=12
gen jwtdtot=r(sum_w)
sum ind [aw=indpxui_xw] if month>=1 & month<=12
gen kwtdtot=r(sum_w)
replace wts=indpxui_xw*(jwtdtot/kwtdtot) if month>=1 & month<=12

For the purpose of the research I am working on, I am using the equivalised household income and other variables referring to parental occupation, education and place of birth.

Since I am using it together with EUSILC 2019 for different EU countries, I was comparing the weights with the weights in EUSILC. While the sum of the weights in the latter equals on average the 80% of the real population in each country, the sum of weights of the dataset I created for UK 2019 (with the merge of wave 10 and 11) gives a number way lower than the census 2019 UK population.

Could you please help me understanding how those weights are constructed, which characteristics of the population they consider, whether they can comparable to ones in EUSILC and whether the procedure I followed to merge the two waves is correct.
Many thanks in advance for the support!