If you satisfied the RMD with the distribution the amount is not important ... just choose the all was RMD and move on ... if you did not take the full RMD then you need the amount required.
What type of retirement account? if a pension or account that you receive periodic payments from then the box 1 amount is the RMD amount.
If an IRA then the RMD must be calculated based on your age and the 2018 year end value of all Traditional IRA accounts combined.
I hope it's as simple as box 1 = RMD for periodic payments.
Virtually all pension plans in existence today fall under section 401 of the tax code and they all require RMD's after age 70 1/2. The question is just to be sure that the requirement was met. If you receive periodic (monthly) payments from any pension plan you can be assured that the custodian of the plan is meeting the requirements so you can safely answer "yes" to the question.
The answer to the question does not go on your tax return, it is simply to make sure you do not owe any penalty for not taking the RMD.
https://ttlc.intuit.com/replies/3302117