When filling paperwork for a new job, the 2019 W4 Page 3 line 1 (2nd 1/2 of page) asks for "estimate of 2018 itemized deductions," should I bother filling this line?

[jacmsim]

I am single, none of the credits from Pub. 505 apply to me, and I took the standard deduction ($12,000) when filing my 2018 taxes last month, even though I had my donations and medical payments itemized. Student Loan Interest $1000, and Charitable Contributions/Donations $500 came out to about $1500. Now I am filling out the paperwork for a new job, on the "Form W-4 (2018) Page 3 Line 1" under Deductions, Adjustments, and Additional Income Worksheet, it asks for "an estimate of 2018 itemized deductions" and line 2 is the standard deduction ($12,000). Line 3 subtracts line 1 from line 2. Line 4 asks for Pub. 505 additional deductions (for me, $0). And Line 5 adds Line 3 and 4. So my question is: should I put an estimate $1500 on line 1?
12,000 - 1,500 = 10,500
+$10 in nonwage income
10,510 / $4,150 (this # given on W4) = 2.5 "Drop any fraction" = 2
"Add Line H (Personal Allowances, for me that value 2) above" = 4 ends up on line 10?

OR

12,000 - 0 = 12,000
+$10 nonwage income = 12,010
12,010 / 4150 = 2.8 "drop fraction" = 2
so my line 10 should still be 4?

I guess it's the same either way but I don't remember needing to do this before so I want to make sure I do it right the 1st time.

[marvahb]

Unless you expect to have Itemized Deductions greater than the standard Deduction allowed ($12,200 for 2019), it is okay to skip Line 1.  

The worksheet is helpful to taxpayers who will have in excess of the $12,200 in itemized deductions, adjustments to income (IRA deduction, deductible part of self-employment tax, etc.), and non wage income (alimony, business income reported on Schedule C, income received on 1099-Rs, rental income, etc.).