dl_bandwidth is on Megahertzs, not on Megabytes, is the bandwidth than Carrier is warrantied to you.
you can use this web site to calculate the speed based on that info:
With that configuration (band: 3, dl_bandwidth: 20Mhz) you can get this results:
Band: 1800MHz, Uplink: 1710-1785MHz, Downlink: 1805-1880MHz
50Mbps ↓ & 25Mbps ↑