Micro Seiki ma-505 x is a low or heavy tonarm?

Well, thank you again, but I found this picture

where it is said that for Ma 505 is ...; 7 gr.

Here is the link ..... I hope it is ok

No, I can not  add this link .... any way it is a micro seiki brochure where it is said that ma 505 effective mass is 7 gr.

If you read this it states that the 505 has an effective mass of 14.5 grams. It might be that the 7 gram mass information that you have is not including the weight of the head shell!

MA-505 Denon 103 Project — Micro (micro-seiki.org)

The effective mass of a tone arm is effected by the location of it’s counterweight. Increasing the distance of the c/w from the arm’s bearings increases the arm’s effective mass. To decrease an arm’s e/m, add weight to it (wheel-balancing stick-on lead weights work) and move it closer to the bearings. To increase it of course do the opposite.

The Groovetracer company makes an excellent after-market counterweight for Rega arms, and it comes with an assortment of different screw-in weights. That allows the same arm to be used with a variety of pickups featuring different suspension compliances.