It is normal that often the output size is greater than the source. 85% is a high value for H.264 or HEVC. I see you are using NVENC hardware encoder, and I do not think this supports the lossless mode of H.264. So, it probably reject some option provided and returned to some default that is lower than 85%. We do not have logic that validates every combination of parameters in Export > Advanced especially in conjunction with every implementation of hardware encoder.