Canon EOS REBEL T7i Instruction Manual page 154

g: Setting the ISO Speed for Still PhotosN
3 Setting the Maximum ISO Speed for [AUTO]N
For ISO Auto, you can set the maximum ISO speed limit within
ISO 400 - ISO 25600.
154
Under the [z2] tab, select [zISO
Auto], then press <0>. Select the ISO
speed, then press <0>.