When writing for piano, composers very often notate a musical intention rather than precise playing instructions. We're being told that Schumann feels there are four musical 'voices' here, and had he been scoring for four actual individual instruments he might have done this.
A pianist will actually play this. Does being made aware of Schumann's concept make any audible difference? Maybe, just a little!
You'll also notice that Schumann dovetails the inner notes, asking the r and l hands to overlap. This would be worth doing if there WERE different instruments playing each layer of the music. Whether it makes a jot of difference on piano is debatable.
But I quite like that Schumann thought orchestrally, even in his piano solo music.
(I see I've misprinted the pickup note. Should be a C. Sorry.)