2 different size needles used in pattern

Hello all thanks in advance for any help. I have a pattern that calls for you to use size 8 needles and size 6 needles. Now they want you to get gauge with the size 8’s. If I have to go up in needle size to get the guage. Would the smaller size needles remain the same size since IM not using them to get gauge? Or would I need to use a bigger size in place of those to?

Since your pattern calls for a 6 and an 8 needle and the 6 is 2 sizes down from the 8, use a needle size that is 2 sizes down from the needle size you are using to get gauge.