$1-3 Limit... turning stone question

[skitzo444]

It was my first B&M trip ever and I went to Turning Stone about a month ago. To get a feel for the room I bought 100 and sat down at a $1-3 LIMIT. After playing for a few hands I noticed you could bet or raise in an incriment BETWEEN 1-3. I thought this was odd b/c it was not a spread game or anything. Later on when playing 3-6 it was a normal limit structure. What's this about?