what is mean <C-+>?

[I-Want-ToBelieve]

size-matters.nvim/lua/size-matters/init.lua

Line 48 in bc5ae8d

map("n", "<C-+>", function() M.update_font("grow") end, { desc = "Increase font size" })

ctrl and + ?

[ttytm]

Hey, sorry for the delayed response. I didn't get a notification about an issue being opened.

Yes, it's Ctrl and +. Which usually is:
Ctrl+Shift+=