Why is my SFE Independent Student Application so low?

My partner applied for student finance at the end of March as an independent student.

Having worked for the past three years they were aware that they would be required to provide evidence in the form of a P60 or other supporting documents.

They sent off the application without uploading this information and were prompted a few days later that it was required. With the aim of doing this over the weekend they started collating the required paperwork.

Two days ago they received a letter confirming the student finance figure for the year at a value of half what was originally projected. This is both a surprise and worry as we are both unsure if this can now be changed.

Will uploading these documents to the application change anything now?

Is it best to call SFE?

Does SFE just process incomplete applications and reassess once evidence is provided?