Is it incorrect to omit the "to" after the object after "round" like "Round your answer one decimal place"?

I came across a math homework assignment that said,

"Round your answer one decimal place."

Interestingly, they decided to not omit the "to" in another phrasing:

"Round your answer to two decimal places."

I wonder if the "to" is optional. Personally, omitting the "to" sounds awkward to me, but I'm not sure if it's a personal preference or a general guideline.

The assignment is published on an official website called WebAssign, owned by Cengage, so it's not a single instructor handwriting/hand-typing these. These assignments are the standards of homework that are required in some courses in colleges like math and physics courses.

Suppose I have 3.14159.
In order to round it one decimal place, I would round it to 3.1416, that is one less place than before.
In order to round it to one decimal place, I would round it to 3.1, that is there is one decimal place left.