Hi

I'm using STAR to perform alignment and my goal is to do the DEG analysis in the future. The parameter I set up as follows:


Step 1:
```
                       STAR --runThreadN 12 \
                                 --runMode genomeGenerate \
                                 --genomeDir genomedir \
                                 --genomeFastaFiles ./ref/GRCm39.primary_assembly.genome.fa \
                                 --sjdbGTFfile ./ref/gencode.vM27.primary_assembly.annotation.gtf \
                                 --sjdbOverhang 100
```
Step 2:
```
                       STAR --runThreadN 12 \
                                 --runMode alignReads \
                                 --twopassMode None \
                                 --genomeDir genomedir \
                                 --sjdbGTFfile ref/gencode.vM27.primary_assembly.annotation.gtf \
                                 --sjdbOverhang 100 \
                                 --readFilesIn "R1_001_trim.fastq.gz" "R2_001_trim.fastq.gz" \
                                 --readFilesCommand zcat \
                                 --outFileNamePrefix "./align_output/try1_" \
                                 --outSAMtype BAM SortedByCoordinate \
                                 --quantMode GeneCounts
```
But the output of genecount file is a bit weird:
```
N_unmapped	1657081	1657081	1657081
N_multimapping	8053375	8053375	8053375
N_noFeature	12418438	43724858	13355695
N_ambiguous	1629488	39643	430809
ENSMUSG00000102693.2	0	0	0
ENSMUSG00000064842.3	0	0	0
ENSMUSG00000051951.6	49	2	47
ENSMUSG00000102851.2	0	0	0
ENSMUSG00000103377.2	10	0	10
ENSMUSG00000104017.2	13	0	13
ENSMUSG00000103025.2	4	1	3
ENSMUSG00000089699.2	0	0	0
ENSMUSG00000103201.2	2	0	2
ENSMUSG00000103147.2	1	1	0
ENSMUSG00000103161.2	7	0	7
ENSMUSG00000102331.2	20	0	20
ENSMUSG00000102348.2	0	0	0
```

Why the gene index at the first column has ".2" or ".3" in the end? like "ENSMUSG00000102693.2",  Shouldn't be just "ENSMUSG00000102693"? I use reference from Gencode by the way
That's the version number of that ensembl gene ID. When a gene model is changed to an appreciable extent the version number increases.