Does streaming with mobile data attract a lot?

I would like to stream, unfortunately, I only have a very low upload of 1 mb / s and I wanted to ask because I have good LTE reception at home, how much is streaming in 720p on Twitch in about four hours

That depends entirely on your set bit rate. Twitch recommends a bit rate of 3 Mbit / s for 720p30. That is 0.375 MB / s or 1.35 GB / h. With four hours you would have a data consumption of 5.4GB. But you can also set your bit rate lower. With this formula you can calculate your data usage:

((Bit rate (in Mbit / s) / 8) * 60 * 60 * 4) / 1000 = data consumption in four hours in GB

Source: https://stream.twitch.tv/encoding/