USCIS does not evaluate the I-134 in a k1 visa process. The Consular Officer does that. Your W2 is not relevant to your stated current income. For an employed person, current income is calculated by taking the gross income for a full pay period times the number of pay periods in a full year (going forward). You then document the income with that same pay stub. Later, when you adjust status and provide an I-864, current income is calculated and documented the same way. At that time, yes, USCIS can and will do the same calculation and recognize the correct current income.