48T is only about 4% bigger than 46T. Rear gear shifts on your cassette range from about 8% to 18%. So the number of cogs you could drop down on the cassette is... about half to one-quarter of one cog, depending on where you currently are in the cassette.

If you're going to try and shift your position on the cassette significantly with a chainring swap, you'll probably want to be looking at a new crankset which supports tiny subcompact chainring sizes. Even if you went all the way down to a 42T big ring, your top gear (42-11) would still be higher than your current second-to-highest gear (48-13), and you'd only move your position on the cassette by about 1 shift.