The header of your vcf file will define what the info attribute DP means. It will look similar to this:
##FORMAT=<ID=DP,Number=1,Type=Integer,Description="Read Depth (only filtered reads used for calling)">
In short, it is read depth at the variant position. If the depth is permitted to be shallower, then the number of calls will increase. This is an interpretation across the two original variant calling parameter settings.
If you are wondering why there are less "very local sensitive variants" compared to "local sensitive variant" with "DP <10", it is probably because the "very local" option is more selective to start with (resulting in fewer calls with depth < 10).
Hopefully this helps, Jen, Galaxy team