Taxation in Switzerland: Mustachian Know-How, Best Practices

I have a question regarding the dividend taxation but i haven’t found a clear answer anywhere in the internet yet.

Assumptions:
Lets assume that I’am EU citizen and Swiss resident (Canton Zug, B permit, Quellensteuer) and I hold US stocks via IB and have filed the W8-BEN (15% WHT). Now i receive CHF 1000 worth of dividends from US companies and IB deducts the witholding tax of 15% for Uncle Sam and I receive CHF 850 to my IB account. At the end of the year I file DA-1 to tell the swiss goverment that i received CHF 1000 dividends and have paid CHF 150 as witholding tax. Tax authorities will then calculate how much do i owe them for that CHF 1000 dividends based on my (marginal) income tax rate. I understand that if my tax rate was 20% swiss tax authoritities would send me a bill of CHF 50 for the missing 5%. However, as canton Zug has so low taxes my income tax rate will be below 15% (let’s assume 10%)

Question:
(1) Will i get that 15% WHT paid to Uncle Sam credited in full or (2) only up to the amount I would owe to the swiss tax authorities?

(1) tax liability to swiss tax authorities on dividend 10% = CHF 100 and missing CHF 50 deducted from my other income taxes; effective tax rate on dividends 10%
(2) tax liability to swiss tax authorities on dividend 10% = CHF 100 and missing CHF 50 gone forever; effective tax rate on dividends 15%

I would highly appreciate if someone knows the answer for this ot can link me to a right source.