sorry I didn't reply sooner, haven't been on DW for quite some time!
Indeed the signature is a quote from Tendai Daishi's (Zhiyi/Zhizhe Dashi) Maka Shikan. In explaining its meaning, I think Brook Ziporyn sums it up quite nicely in the following:
"...the proposition 'there is nothing but mind' does not mean that there is only this one mind and that all other things are just illusory appearances in that mind. Rather, all minds are equally real in all their qualitative difference, but they are also equally all-pervasive, so that no mind or thing has an end. Each mind, each object is 'all there is'. Thus any mind is the only mind, and indeed any any sensation or piece of matter is equally the only thing there is; any determination chosen as a starting point pervades all times and places and is
the substratum into which all else is reducible. (Brook Ziporyn, Evil and/ or/ as the Good, 2000.)
"There are no seperate dharma's in the Three Realms. There is only the operation of the one mind."
"Whoever wishes to benefit beings ought to establish teachings that fit their capacities, expound the dharma in accordance with their capacities, and match the doctrines to them"