gvim options / Settings window cannot write buftype is set e382

I was trying to customize gvim a bit. I see under the Edit menu is an option to change Settings Window. It opens up but then I get the following error.

E382 cannot write, 'buftype' option is set.

How do I write the options I change? Online I see people saying I need to add options to the vimrc file either in ~/.vimrc or /etc/vimrc or /etc/gvimrc. I thought that I would be able to do it directly through the gvim editor, not by adding options to my ~/.vimrc file.

Solution 1:

A serious case of RTFM, on my account. The top few lines explain how to edit it.

" Each "set" line shows the current value of an option (on the left).
" Hit <CR> on a "set" line to execute it.
"            A boolean option will be toggled.
"            For other options you can edit the value.
" Hit <CR> on a help line to open a help window on this option.
" Hit <CR> on an index line to jump there.
" Hit <Space> on a "set" line to refresh it.

I then pressed Enter, and my setting took affect immediately

on line 155
lines   number of lines in the display
    set lines=50