How Are Indel Coded In Vcf Files

Hello,

I have a question concerning how are INDEL coded in VCF files. I have for instance the following file:

CHROM POS ID REF ALT QUAL FILTER

8 18078835 . TTA T 46 PASS

8 18078836 . TA T 138 PASS

How to interpret it as the two positions are following each other (835 and 836)?

And also, how to interpret the QUAL (I thought 100 was the maximum value...)?

Many thanks

Christelle