heartquest,
I too am sorry to hear of Calvins passing,
perhaps we can carry on in his spirit...
this heart might be the spanish one of the group..as I think the heart that points to the dolmen is made by the ones who made the tomb...the spanish just added the "7" saving them a lot of time and work...now this heart with the X has the flavor of the codemakers...notice the right lobe of the heart is thicker, larger, so it seems to me, and I cannot confirm this one, as
I have not seen a heart with an X on it before, but I do know they used pointers for their lines...and but just as old dog has said, this is a distance maker above all, so my guess roman
numeral for 10..master of the understatement there huh?lol
this seems to say follow the line of the X on the biggest side [lobe] of the heart, you might want to note this compass bearing, perhaps it is a cardinal point, which will confirm it..
good luck and nice find of this group of signs, a tantalizing mystery will unfold if you can decode the marks
rangler

edit:distance is 30 yards [90ft] divided by X [ten] = 3 measurement units, so ponder me this
friend and foe alike, what measurement unit is equal, is it rods at 5.5 yards[165 ft]? nope,...
chain ? cordel , braza, yard, meter ,ect ...questions, no wonder they call it a quest~!!
its a quest of questions~!!...where is my calculator...or an app for one..hmm lol I wonder if they have an app for plotting shadows...
rangler