SRAM 5.0 Cassette

My bike has an SRAM 5.0 8spd Cassette. I was wondering if anybody else has noticed a rather big jump
when switching from about the 4th to 3rd cog. I find it a large skip for a cassette, and it's
somewhat troubling when you're climbing. It's not a problem with wear, or my derailleurs because the
bike is brand new. Just looking at the cogs shows a visible difference in size. Do they manufacture
the freewheel this way to facilitate shifting or what?

Cheers,

Peter