Below is my code

library(ChIPseeker)
library(TxDb.Hsapiens.UCSC.hg19.knownGene)
txdb <- TxDb.Hsapiens.UCSC.hg19.knownGene

files <- getSampleFiles()

options(ChIPseeker.downstreamDistance = 1000)
peakAnno <- annotatePeak(files[[4]], tssRegion=c(-3000, 3000),
                         TxDb=txdb)
plotAnnoPie(peakAnno)

options(ChIPseeker.downstreamDistance = 10)
peakAnno <- annotatePeak(files[[4]], tssRegion=c(-3000, 3000),
                         TxDb=txdb)
plotAnnoPie(peakAnno)

I find that no matter what number I enter in options(ChIPseeker.downstreamDistance = ). The percent of downstream is same, But the number in plot indeed change.