Layout change for Blurb Book

Hello.

is how my pages look in the book module in LR5.

What I want to do now is making the gap horizontally smaller, so I have the group of six portrait photographs closer together. I managed to get this far, but just don't find how to move them horizontally towards each other.

I was able to move them vertically with Cell padding. Left value is 30 pt, right 14 and top 74. Bottom is zero value.

I think that I need to change one of the values to a certain number...

This might look very simple and easy to do for some of you, but I have had a couple of total sedations due to being sick  and my logical reasoning has gone down the drain.

Can anyone point me in the right direction? I watched Julianne Kost her video but it does not really help me for that last bit of information I need.

I will also ask around on the Blurb forum...

Anyone?

Thanks in advance

Catherine